Iran is on the “cusp of a full-scale confrontation with the enemy”, an Iranian military commander has claimed, as sabre-rattling between Washington and Tehran intensified.

As US politicians from both major parties urged Donald Trump to de-escalate tensions between the countries, a commander of Iran’s highly-trained Revolutionary Guards warned that Tehran was prepared for any conflict that may arise.

“We are on the cusp of a full-scale confrontation with the enemy,” said Maj Gen Hossein Salami, who was named head of the force last month.

The Fars news agency quoted him as saying: “This moment in history, because the enemy has stepped into the field of confrontation with us with all the possible capacity, is the most decisive moment of the Islamic revolution.”

The comments came after several days of mounting tension between the two countries, with the US sending additional troops and equipment to the region. It has done so amid claims that US and coalition troops in Iraq and Syria, who are fighting the remnants of Isis, are at increased risk from Iran, or Iranian-backed militias.

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Iran has denied the claim and said the US is seeking to drag it into an unnecessary war.

On Tuesday, a British general who is second in command of strategy and information for the coalition operation named Inherent Resolve, Maj Gen Chris Ghika, told reporters at the Pentagon there was no evidence of an increased threat. “No, there has been no increased threat from Iranian-backed forces in Iraq and Syria,” he said.

The US military central command later issued a statement saying the general’s comments were not accurate.

“Recent comments from [Gen Ghika ] run counter to the identified credible threats available to intelligence from US and allies regarding Iranian backed forces in the region,” it said.

On Wednesday it emerged the US had ordered the departure of non-emergency American employees from its diplomatic missions in Iraq in another apparent show of concern about possible threats.

Helicopters were said to have been seen taking off throughout the day from the vast embassy compound near the Tigris River, carrying staff out.

In Washington, both Republicans and Democrats urged caution. Mr Trump reimposed sanctions on Iran last year after pulling America out of the multi-party nuclear deal.

Congressional leaders will get more information about the situation on Thursday during a confidential briefing with Trump officials, Politico reported.

“It’s close to inconceivable that the president, the administration would consider a war with Iran,” said Utah senator Mitt Romney, a Republican critic of the president. “The president made it clear when he ran for president that one of the worst foreign policy mistakes in American history was the decision to go to war with Iraq.”

Meanwhile, House speaker Nancy Pelosi reportedly said: “Let me say that we have to avoid any war with Iran.”