Sources close to Mr Vance told The Washington Post that if the conflict with Iran lasts for months, it could pose a political problem for whoever secures the Republican presidential nomination in 2028. However, Mr Vance still hasn’t decided whether he will run, the outlet’s sources also said.

The vice-president has publicly voiced his support for Mr Trump’s war with Iran. While Mr Vance has previously criticised prolonged foreign involvement, he has also pushed back on suggestions that his past comments indicate he’s not aligned with the president.

“I know what you’re trying to do,” Mr Vance said Monday, when confronted about his previous statements on American interventionism.

“You’re trying to drive a wedge between members of the administration, between me and the president. What the president has said consistently, going back to 2015, and I agreed with him, is that Iran should not have a nuclear weapon.”

Still, the president has said Mr Vance was “maybe less enthusiastic” at the beginning of the conflict.

“We get along very well on this,” Mr Trump told reporters last week. “He was, I would say, philosophically a little bit different than me. I think he was maybe less enthusiastic about going, but he was quite enthusiastic.

“But I felt it was something we had to do. I didn’t feel we had a choice. If we didn’t do it, they would have done it to us.”

The Trump administration has maintained that the two men are aligned on the issue

Mr Vance also reportedly met with Joe Kent, the former director of the National Counterterrorism Centre, who resigned over the war with Iran. The vice-president urged him to “go quietly” and not make his resignation a “big thing,” a US official told The Washington Post.

The Independent has contacted Mr Vance’s office for comment.

This comes after Politico reported that Mr Vance privately expressed scepticism about the US attacking Iran before Mr Trump made his final decision. Still, the Trump administration has maintained that the two men are aligned on the issue.

White House spokesperson Anna Kelly previously told The Independent that “efforts to drive a wedge between President Trump and vice-president Vance are totally misguided.”

Mr Vance’s spokesperson Taylor Van Kirk told Politico the vice-president is “a proud member of the President’s national security team” and “keeps his counsel to the President private”.

Others have also speculated about the conflict’s impact on the 2028 election, including Marjorie Taylor Greene, a former Republican lawmaker who resigned from her House seat late last year after a public falling-out with Mr Trump.

When asked by CNN’s Pamela Brown if the Iran war could hurt the vice-president’s chances of becoming Mr Trump’s successor, the ex-lawmaker said: “The longer it goes on, it definitely does hurt JD Vance.”