The US will order more troops to the Middle East, Donald Trump has said, despite just a day earlier saying he thought further deployments in the region were unnecessary.

Mr Trump said around 1,500 troops would be sent amid rising tensions with Iran. Congressional aides confirmed that Congress was notified of the new plan before it was announced.

"We want to have protection. The Middle East, we're going to be sending a relatively small number of troops," Mr Trump told reporters at the White House before boarding a plane for Japan. "Mostly protective. Some very talented people are going to the Middle East right now. And we'll see how – we'll see what happens."

A defence official later claimed that the actual number of incoming troops was 900, which will be to added to 600 troops whose deployment in the region will be extended.

The announcement comes at the end of a week in which several numbers were floated for troop increases in the region.

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

On Thursday, the acting defense secretary, Patrick Shanahan, denied reports that between 5,000 to 10,000 US troops could be sent to defend against the potential threat from Iran.

"There is no 10,000, there's no 5,000, and that's not accurate," he told reporters.

Representative Adam Smith, who serves as the House Armed Services Committee Chairman, issued a statement calling the increase in troops an “unsettling” move.

"Without a clearly articulated strategy, adding more personnel and mission systems seems unwise, and appears to be a blatant and heavy-handed move to further escalate tensions with Iran," Mr Smith said.