At a meeting of President Donald Trump’s top national security aides last Thursday, Acting Defense Secretary Patrick Shanahan presented an updated military plan that envisions sending as many as 120,000 troops to the Middle East should Iran attack US forces or accelerate work on nuclear weapons, administration officials said.

The revisions were ordered by hard-liners led by John Bolton, Mr Trump’s national security adviser. It does not call for a land invasion of Iran, which would require vastly more troops, officials said.

The development reflects the influence of Mr Bolton, one of the administration’s most virulent Iran hawks, whose push for confrontation with Tehran was ignored more than a decade ago by President George W. Bush.

It is highly uncertain whether Mr Trump, who has sought to disentangle the United States from Afghanistan and Syria, ultimately would send so many US forces back to the Middle East.

It is also unclear whether the president has been briefed on the number of troops or other details in the plans. On Monday, asked if he was seeking regime change in Iran, Mr Trump said: “We’ll see what happens with Iran. If they do anything, it would be a very bad mistake.”

How the British media covered the Iraq War Show all 6 1 /6 How the British media covered the Iraq War How the British media covered the Iraq War Daily Mirror, 6 January 2003 How the British media covered the Iraq War The Guardian, 21 March 2003 How the British media covered the Iraq War The Daily Mail, 22 March 2003 How the British media covered the Iraq War Daily Telegraph, 21 March 2003 How the British media covered the Iraq War The Sun, 20 March 2003 How the British media covered the Iraq War

There are sharp divisions in the administration over how to respond to Iran at a time when tensions are rising about Iran’s nuclear policy and its intentions in the Middle East.

Some senior US officials said the plans, even at a very preliminary stage, show how dangerous the threat from Iran has become. Others, who are urging a diplomatic resolution to the current tensions, said it amounts to a scare tactic to warn Iran against new aggressions.

European allies who met with Secretary of State Mike Pompeo on Monday said that they worry that tensions between Washington and Tehran could boil over, possibly inadvertently.

More than a half-dozen US national security officials who have been briefed on details of the updated plans agreed to discuss them with The New York Times on the condition of anonymity. Spokesmen for M<r Shanahan and Gen. Joseph Dunford Jr, the chairman of the Joint Chiefs of Staff, declined to comment.

The size of the force involved has shocked some who have been briefed on them. The 120,000 troops would approach the size of the US force that invaded Iraq in 2003.

Iran's Foreign Minister tells NBC News that starting a war with Iran would be ‘suicidal'

Deploying such a robust air, land and naval force would give Tehran more targets to strike, and potentially more reason to do so, risking entangling the United States in a drawn out conflict. It also would reverse years of retrenching by the US military in the Middle East that began with President Barack Obama’s withdrawal of troops from Iraq in 2011.

But two of the US national security officials said Mr Trump’s announced drawdown in December of American forces in Syria, and the diminished naval presence in the region, appear to have emboldened some leaders in Tehran and convinced the Islamic Revolutionary Guards Corps that the United States has no appetite for a fight with Iran.

Several oil tankers were attacked or sabotaged off the coast of the United Arab Emirates over the weekend, raising fears that shipping lanes in the Persian Gulf could become flashpoints. “It’s going to be a bad problem for Iran if something happens,” Mr Trump said on Monday, asked about the episode.

Emirati officials are investigating the apparent sabotage, and US officials suspect that Iran was involved. Several officials cautioned, however, that there is not yet any definitive evidence linking Iran or its proxies to the attacks. An Iranian Foreign Ministry spokesman called it a “regretful incident,” according to a state news agency.

In Brussels, Mr Pompeo met with the foreign ministers of Britain, France and Germany, cosignatories of the 2015 Iran nuclear deal, as well as with the European Union’s foreign policy chief, Federica Mogherini. He did not speak to the media, but the European officials said they had urged restraint upon Washington, fearing accidental escalation that could lead to conflict with Iran.

“We are very worried about the risk of a conflict happening by accident, with an escalation that is unintended really on either side,” said Jeremy Hunt, the British foreign secretary.

The Iranian government has not threatened violence recently, but last week, President Hassan Rouhani said Iran would walk away from parts of the 2015 nuclear deal it reached with world powers. Mr Trump withdrew the United States from the agreement a year ago, but European nations have urged Iran to stick with the deal and ignore Trump’s provocations.

Donald Trump withdraws from nuclear deal with Iran

The high-level review of the Pentagon’s plans was presented during a meeting about broader Iran policy. It was held days after what the Mr Trump administration described, without evidence, as new intelligence indicating that Iran was mobilizing proxy groups in Iraq and Syria to attack US forces.

As a precaution, the Pentagon has moved an aircraft carrier, B-52 bombers, a Patriot missile interceptor battery and more naval firepower to the Gulf region.

At last week’s meeting, Mr Shanahan gave an overview of the Pentagon’s planning, then turned to Dunford to detail various force options, officials said. The uppermost option called for deploying 120,000 troops, which would take weeks or months to complete.

Photographer Chris Hondros: How I captured Iraq Show all 9 1 /9 Photographer Chris Hondros: How I captured Iraq Photographer Chris Hondros: How I captured Iraq 18273.bin 2003 Getty Images Photographer Chris Hondros: How I captured Iraq 18276.bin 2003 Getty Images Photographer Chris Hondros: How I captured Iraq 18277.bin 2003 Getty Images Photographer Chris Hondros: How I captured Iraq 18274.bin 2004 Getty Images Photographer Chris Hondros: How I captured Iraq 18275.bin 2004 Getty Images Photographer Chris Hondros: How I captured Iraq 18278.bin 2005 Getty Images Photographer Chris Hondros: How I captured Iraq 18279.bin 2006 Getty Images Photographer Chris Hondros: How I captured Iraq 18280.bin 2006 Getty Images Photographer Chris Hondros: How I captured Iraq 18281.bin 2007 Getty Images

Among those attending Thursday’s meeting were Mr Shanahan; Bolton; Dunford; Gina Haspel, the CIA director; and Dan Coats, the director of national intelligence.

“The president has been clear, the United States does not seek military conflict with Iran, and he is open to talks with Iranian leadership,” Garrett Marquis, a National Security Council spokesman, said Monday in an email. “However, Iran’s default option for 40 years has been violence, and we are ready to defend US personnel and interests in the region.”

The reduction of forces in the Middle East in recent years has been propelled by a new focus on China, Russia and a Great Powers competition. The most recent National Defense Strategy — released before Mr Bolton joined the Mr Trump administration — concluded that while the Middle East remains important, and Iran is a threat to American allies, the United States must do more to ensure a rising China does not upend the world order.

As recently as late April, a US intelligence analysis indicated that Iran had no short-term desire to provoke a conflict. But new intelligence reports, including intercepts, imagery and other information, have since indicated that Iran was building up its proxy forces’ readiness to fight and was preparing them to attack U.S. forces in the region.

The new intelligence reports surfaced on the afternoon of 3 May, Shanahan told Congress last week. On 5 May, Mr Bolton announced the first of new deployments to the Persian Gulf, including bombers and an aircraft carrier.

It is not clear to US intelligence officials what changed Iran’s posture. But intelligence and Defense Department officials said American sanctions have been working better than originally expected, proving far more crippling to the Iranian economy — especially after a clampdown on all oil exports that was announced last month.

Also in April, the State Department designated the Revolutionary Guards a foreign terrorist organisation over objections from Pentagon and intelligence officials who feared reprisals from the Iranian military.

While much of the new intelligence appears to have focused on Iran readying its proxy forces, officials said they believed the most likely cause of a conflict will follow a provocative act, or outright attack, by the Revolutionary Guards’ navy. The Guards’ fleet of small boats has a history of approaching US Navy ships at high speed. Revolutionary Guards commanders have precarious control over their ill-disciplined naval forces.

The Islamic Republic of Iran 40 years on Show all 20 1 /20 The Islamic Republic of Iran 40 years on The Islamic Republic of Iran 40 years on Women praying during Ashura festivities in Yazd in February Jan Schneider The Islamic Republic of Iran 40 years on Cars cemented in at the Holy Defence Museum-Garden in Khorramshahr – in 1980 occupying Iraqi forces used such formations to deter paratrooper landings Jan Schneider The Islamic Republic of Iran 40 years on Women on the Si-o-se-pol bridge over the Zayanderude river in Esfahan Jan Schneider The Islamic Republic of Iran 40 years on Iranian tourists at Vank cathedral in the Armenian quarter in the city of Esfahan Jan Schneider The Islamic Republic of Iran 40 years on A reddened fountain in Yazd – a national motif recalling the countries ‘martyrs’ Pictures by Jan Schneider The Islamic Republic of Iran 40 years on Prayers before a list naming the fallen of the Iran-Iraq war in Tehran Jan Schneider The Islamic Republic of Iran 40 years on In a museum in central Tehran, a wax figure of Ayatollah Khomeini Jan Schneider The Islamic Republic of Iran 40 years on Carom billiards in Tehran Jan Schneider The Islamic Republic of Iran 40 years on Nearly two thirds of Iran’s population is under-30 Jan Schneider The Islamic Republic of Iran 40 years on Sanctions are exacerbating poverty Jan Schneider The Islamic Republic of Iran 40 years on Young people are adept at catching moments of freedom, such as this one in the capital Jan Schneider The Islamic Republic of Iran 40 years on At an art auction in Tehran, the wealthy turn out Jan Schneider The Islamic Republic of Iran 40 years on Propaganda murals are everywhere Jan Schneider The Islamic Republic of Iran 40 years on Tehranis love their outdoor spaces too Jan Schneider The Islamic Republic of Iran 40 years on The hypersaline waters of Lake Urmia are fast diminishing – Iran faces ecological catastrophe Jan Schneider The Islamic Republic of Iran 40 years on A martyr is depicted outside the huge Beheshte-e-Zahra cemetery in Tehran Jan Schneider The Islamic Republic of Iran 40 years on A guard naps outside Iran’s foremost tourist attraction – the ancient ruins of Persepolis Jan Schneider The Islamic Republic of Iran 40 years on Memorial to Iranian pilgrims who died during a stampede in Mecca 1987 Jan Schneider The Islamic Republic of Iran 40 years on The martyr fixation on display in the southern city of Shush Jan Schneider The Islamic Republic of Iran 40 years on Emamzadeh Saleh mosque in Shemiran, Tehran Jan Schneider

Part of the updated planning appears to focus on what military action the United States might take if Iran resumes its nuclear fuel production, which has been frozen under the 2015 agreement. It would be difficult for the Mr Trump administration to make a case that the United States was under imminent nuclear peril; Iran shipped 97% of its fuel out of the country in 2016, and currently does not have enough to make a bomb.

That could change if Iran resumes enriching uranium. But it would take a year or more to build up a significant quantity of material, and longer to fashion it into a weapon. That would allow, at least in theory, plenty of time for the United States to develop a response — like a further cutoff of oil revenues, covert action or military strikes.

The previous version of the Pentagon’s war plan included a classified subset code-named Nitro Zeus, a cyberoperation that called for unplugging Iran’s major cities, its power grid and its military.

The idea was to use cyberweapons to paralyze Iran in the opening hours of any conflict, in hopes that it would obviate the need to drop any bombs or conduct a traditional attack. That plan required extensive presence inside Iran’s networks — called “implants” or “beacons” — that would pave the way for injecting destabilising malware into Iranian systems.

Two officials said those plans have been constantly updated in recent years.

Revolution in Iran: In pictures Show all 11 1 /11 Revolution in Iran: In pictures Revolution in Iran: In pictures A demonstration against the Shah in 1979 Getty Revolution in Iran: In pictures Armed women on guard in one of the main squares in Tehran at the beginning of the Iranian Revolution Getty Revolution in Iran: In pictures Demonstrators hold a poster of Ayatollah Ruhollah Khomeini, in January 1979, in Tehran, during a demonstration against the Shah AFP/Getty Revolution in Iran: In pictures Iranian rebels pose with a U.S. flag they bayonetted upside down on trees at Sultanabad Garrison northeast of Tehran on February 12 2019 AP Revolution in Iran: In pictures A gun battle in Khorramshahr during the revolution, 1979 Getty Revolution in Iran: In pictures Ayatollah Khomeini's supporters demonstrate in the streets of Tehran against the Shah among tear gas. The "black friday" caused the death of 200 people according to the Iranian government, 2000 according to the opposition, September 8 1978 AFP/Getty Revolution in Iran: In pictures Women wearing the traditional Chador demonstrate in the streets of Tehran against the Shah on September 7 1978 AFP/Getty Revolution in Iran: In pictures Demonstrators in Tehran calling for the replacement of the Shah of Iran during the Iranian Revolution, 1979. They carry placards depicting Ayatollah Mahmoud Talaghani, one of the leading revolutionaries Getty Revolution in Iran: In pictures Ayatollah Khomeini's supporters demonstrate in the streets of Tehran against the Shah. The "black friday" caused the death of 200 people according to the Iranian government, 2000 according to the opposition, September 8 1978 AFP/Getty Revolution in Iran: In pictures Thousands of the Ayatollah Khomeini's supporters on the streets of Tehran calling for the religious leader's return in January 1979 Getty Revolution in Iran: In pictures The Iranian Islamic Republic Army demonstrates in solidarity with people in the street during the Iranian revolution. They are carrying posters of the Ayatollah Khomeini, the Iranian religious and political leader Getty

But even a cyberattack, without dropping bombs, carries significant risk. Iran has built up a major corps of its own, one that successfully attacked financial markets in 2012, a casino in Las Vegas and a range of military targets. US intelligence officials told Congress in January that Iranian hackers are now considered sophisticated operators who are increasingly capable of striking US targets.

Since Mr Bolton became national security adviser in April 2018, he has intensified the Mr Trump administration’s policy of isolating and pressuring Iran. The animus against Iran’s leaders dates back at least to his days as an official in the George W. Bush administration. Later, as a private citizen, Mr Bolton called for military strikes on Iran, as well as regime change.

The newly updated plans were not the first time during the Mr Trump administration that Mr Bolton has sought military options to strike Iran.

Iranians take to streets on anniversary of revolution

This year, Defense Department and senior US officials said Mr Bolton sought similar guidance from the Pentagon last year, after Iranian-backed militants fired three mortars or rockets into an empty lot on the grounds of the US Embassy in Baghdad in September.

In response to Mr Bolton’s request, which alarmed Jim Mattis, then the defense secretary, the Pentagon offered some general options, including a cross-border airstrike on an Iranian military facility that would have been mostly symbolic.

But Mr Mattis and other military leaders adamantly opposed retaliation for the Baghdad attack, successfully arguing that it was insignificant.