Trump has repeatedly criticised British Prime Minister Keir Starmer, most recently suggesting he helped "ruin" the countries' historically close relationship after London blocked the US's initial use of British bases to attack Iran.
In a post on Truth Social, Trump said he "will remember" the lack of British support during the conflict with Iran.
"The United Kingdom, our once Great Ally, maybe the Greatest of them all, is finally giving serious thought to sending two aircraft carriers to the Middle East," Trump said.
"That's OK, Prime Minister Starmer, we don't need them any longer - But we will remember. We don't need people that join Wars after we've already won!"
The post comes after the British Ministry of Defence said on Saturday it was preparing the Prince of Wales aircraft carrier for possible deployment.
But no final decision has been taken about whether to deploy the aircraft carrier to the Middle East, a British official said.
Starmer has defended his decision not to allow US forces to use British bases to support initial strikes on Iran, saying he needed to be satisfied any military action was legal and well planned.
He later granted US forces permission to use British bases for what he called defensive strikes against Iranian missiles in storage depots or launchers.
Asked about Trump's comments, British foreign minister Yvette Cooper told Sky News on Sunday: "The thing I've learned doing this job is that you have to focus on substance and not on social media posts."
Ms Cooper said the UK would not "do things in terms of the rhetoric or hyperbole".
"We're going to do things on really practical, calm, steady decision-making," she said.
"Because I think that actually the British character more widely is to do things in a serious and steady way."
Starmer earlier in 2026 criticised Trump's desire to buy Greenland and said his comments that European troops avoided frontline combat in the war in Afghanistan were "frankly appalling".
