Iranian missiles could easily hit US ships in the Gulf, and any conflict would threaten global energy supplies, a senior Iranian military official has said.

As tensions simmered on Friday, Tehran blamed the US for an escalating regional crisis that western intelligence officials fear could lead to open conflict.

“If a war happens, the world’s energy supply will suffer,” Gen Saleh Jokar, deputy commander of the Revolutionary Guards, said on Friday. He added: “Iran’s short-range missiles can easily reach present [US] warships in the Persian Gulf.”

Iranian military leaders say the Trump administration’s “maximum pressure” approach, which includes crippling sanctions on Tehran’s economy and a unilateral pullout from a nuclear deal, has forced an inevitable reaction.

On Thursday Maj Gen Hossein Salami, commander of the Revolutionary Guards and the country’s overall military leader, said the two countries were on the verge of a full-scale confrontation. “This is the most decisive moment for the Islamic revolution because the enemy has come to the battlefield with all of its capacities at its disposal,” he told a meeting of subordinates.

The economic stranglehold in particular is causing hardship inside Iran and squeezing its ability to sustain a regional proxy network that has been an essential pillar of its foreign policy projection. Before the latest flare-up, Iran’s president, Hassan Rouhani, said parts of the country were facing the most severe shortages since the height of the Iran-Iraq war.

The Guardian reported on Thursday that Iran’s most prominent general, Qassem Suleimani, had recently called a meeting in Baghdad in which he told Iranian-backed Iraqi militias to “prepare for proxy war”. Intelligence sources have said regional affiliates were “effectively sent to battle stations”.

“This wasn’t just in Iraq,” one official said. “The rest of their friends were told to wait for instructions. So far that hasn’t happened to the Iraqi proxies, and there’s a lot of effort going into ensuring that it doesn’t.”

Tensions have remained high since last Sunday when four ships, including two Saudi oil tankers, were hulled off the UAE coast. The UK and US believe Iran was ultimately behind the ships’ sabotage. The following day, Iranian-allied rebels in Yemen used drones to attack two Saudi pipelines.

Intelligence agencies have been monitoring the activities of the Quds force for an extended period to calibrate the extent of their influence on friendly militias operating in Iraq and Syria, with the focus intensifying in recent weeks as the Iran nuclear deal has unravelled.

British sources said the key was to ensure that “no miscalculation” was made in response to the developments in the region, and that the threat was neither under- nor overrated at a time when some voices are pushing for an escalation of US sanctions or even military action against Iran.

On Thursday Saudi state media called for “surgical strikes” against Iranian targets in response to the attack on the oil tankers. One intelligence official who spoke to the Guardian said the Saudis had specifically asked Washington whether it would act to defend their interests.

Britain has been eager to demonstrate it is acting in step with the US since a disastrous Pentagon briefing this week by a senior British officer who unexpectedly claimed there was “no increased threat” from Iranian forces in Iraq and Syria.

The UK has rowed back since, raising the threat level for its forces in the region. On Thursday the foreign secretary, Jeremy Hunt, said the UK “shared the same assessment” of the threat as the Americans, and on Friday the Foreign Office advised against any travel to Iran by British-Iranian dual nationals.

The US and Iran have been engaged in a proxy war for much of the past 15 years, since shortly after the invasion that ousted Saddam Hussein and empowered Iraq’s majority Shias. Militia groups organised under Suleimani’s tutelage evolved into a formidable threat to US forces before the 2011 troop withdrawal. The Pentagon assessed at the time that Shia special groups were responsible for roughly 25% of US battle casualties.

When the war against Isis erupted, the US and Iran fought on the same side at times, with the US air force providing air cover to Shia units operating alongside the Iraqi military in central Iraq and Fallujah.

The detente coincided with Barack Obama’s outreach to Iran, which led to the nuclear deal. The pivot towards Iran came at the expense of Washington’s long-term relationship with Saudi Arabia, which for nearly 40 years had backed a form of Islam that had widely been seen to have underwritten Sunni extremism.

Since the US withdrawal from Iraq, Iran has consolidated its influence among the country’s political class. The Syrian civil war and its spinoffs have given Tehran a new platform on Israel’s doorstep. Iranian moves to entrench military interests in western Syria have been central to the Trump administration’s renewed hostility.

Traditional US allies in Riyadh and Abu Dhabi have long viewed the Iranian leadership as subversive threats in the Sunni Arab world and believe the Obama outreach gave impetus to Iranian expansionism at the expense of existing partnerships.

Additional reporting: Mohammed Rasool