Donald Trump could be pressured to de-escalate tensions in Iran either by military leaders or Republicans in Congress, according to a US national security analyst.

The president issued an expletive-laden rant at Iran over the weekend, threatening to bomb civilian infrastructure unless it opens the oil shipping lane – the Strait of Hormuz – before his self-imposed deadline tonight.

Ben Rhodes, who served as the deputy US national security adviser under Barack Obama, said Trump was operating outside of the usual checks and balances US presidents usually rely on.

He told BBC Radio 4′s Today programme: “It increasingly feels like at times, not all the times but at times, it is one man in one room making decisions or making threats and a government adjusting to that.

“We’re seeing a lack of expertise, a lack of thinking even two steps ahead, and I think that’s probably a sign they’re not following the normal process.”

“It’s kind of frightening really,” Rhodes added, pointing to the senior figures within the first Trump administration who stood up to the president.

Trump said: “This time, on the military side, with the selection of Pete Hegseth, he got the secretary [of defence] he wanted. Someone who principally would just follow Trump’s directive and be something of a spokesperson for them.

“Frankly, I think the checks are going to come from external sources.”

Rhodes suggested now it might all come down to Republicans in Congress who are “terrified about the political unpopularity of this war, from the markets and stock markets Trump pays attention to”.

He said he believes they will have more impact at “restraining Trump” than any process within the Pentagon or government.

Rhodes also claimed he hopes military leaders will pressure the president behind the scenes as Trump continues to threaten “absolute war crimes”.

“It’s a very important test really if the US military is willing to say no to Trump. He didn’t like it when they said no to him in the first term,” Rhodes said.

“There’s no way around the fact that we may be approaching that point because the war itself, I would argue, may be illegal but these things he’s threatening are clear war crimes.”

But the specialist warned Trump has set so many objectives for this war so will be pushing for a victory of some sorts.

“That is not something the Iranians are going to give him, right, because they control the strait,” Rhodes added.

He said they would most likely to have to resolve the war over negotiations with other countries around the table.