Donald Trump has asserted rarely used emergency powers to sidestep congressional objections, and give the green light to an arms deal involving Saudi Arabia and the UAE.

The US secretary of state, Mike Pompeo, told the leaders of several congressional committees the president was claiming a national emergency existed because of a purported threat from Iran and was, as a result, giving permission for 22 arms deals with around $8bn (£6.3bn).

A number of members of congress, which had already voted for the US to terminate its support for Saudi’s military operation against Yemen – a resolution Mr Trump vetoed – fear the weapons could be used in those bombing operations, which have resulted in widespread civilian injuries.

Some legislators had warned earlier this week that Mr Trump, frustrated with congress holding up weapons sales like a major deal to sell Raytheon Co precision-guided munitions to Saudi Arabia, was considering using a loophole in arms control law to go ahead with the sale by declaring a national emergency.

“I am disappointed, but not surprised, that the Trump administration has failed once again to prioritise our long-term national security interests or stand up for human rights, and instead is granting favours to authoritarian countries like Saudi Arabia,” said senator Bob Menendez, the ranking Democrat on the Senate foreign relations committee.

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Republican senator Jim Risch, chairman of the committee, said he had received formal notification of the administration’s intent to move forward with “a number of arms sales”.

Video shows damaged buildings and homes in Yemen village hit by Saudi-led coalition airstrikes

“I am reviewing and analysing the legal justification for this action and the associated implications,” he said.

“President Trump is only using this loophole because he knows Congress would disapprove ... There is no new 'emergency' reason to sell bombs to the Saudis to drop in Yemen, and doing so only perpetuates the humanitarian crisis there,” said senator Chris Murphy.

The White House did not immediately respond to requests for comment.

The state department responded to questions with Mr Pomeo’s memorandum to members of Congress. It failed to respond to a question as to what the US was doing to prevent civilian deaths in Yemen.

In his memorandum to Congress justifying the sale, Mr Pompeo listed years of alleged actions by Iran. “Iranian malign activity poses a fundamental threat to the stability of the Middle East and to American security at home and abroad,” he wrote.

However, Andrew Smith of Campaign Against Arms Trade, a a UK-based activist group, told The Independent: “This unprecedented move shows the terrible depths that Trump and his administration will sink to in order to continue arming and supporting the brutal Saudi regime.

“Saudi forces have inflicted a terrible humanitarian catastrophe on Yemen. It simply would not have been possible without US-made weapons. The arms sales that Trump is pushing today could be used to commit atrocities and abuses for years to come.”