Donald Trump is a “very transactional” president, whose repeated demands on Iran must be seen in this context, one of Keir Starmer’s most senior ministers has said in an unusually blunt UK assessment of relations between the countries.

Asked about the US president’s threats of some sort of retaliation against allies who do not supply ships to try to free up the strait of Hormuz, Pat McFadden, the work and pensions secretary, said the UK was not obliged to agree to every US request.

After Trump again criticised the UK for a perceived lack of enthusiasm in helping the US-Israeli war against Iran, McFadden said it was important to separate the US president’s “rhetoric” from the more important issues.

In an overnight interview with the Financial Times, Trump reiterated his frustration at the UK for not sending ships to the strait of Hormuz, the vital sea freight passage that has been all but closed by Iranian retaliatory attacks.

“It’s only appropriate that people who are the beneficiaries of the strait will help to make sure that nothing bad happens there,” Trump said. “If there’s no response or if it’s a negative response, I think it will be very bad for the future of Nato.”

Asked if he believed Trump might reduce support for Nato if other members did not do as he demanded with Iran, McFadden told Sky News: “Well, that’s the president right there. The quote that you’ve just given has summed him up.

“It’s a very transactional presidency, and our job is to navigate this, to always remember that the friendship between the United States and the United Kingdom runs very deep. It’s a good relationship. It’s enduring, and I think it will outlast all the personalities involved.”

Rather than sending ships, the UK is instead drawing up plans to send minesweeping drones to the strait of Hormuz, amid concerns that complying with Trump’s demand could escalate the crisis.

Asked about this, McFadden said: “The honest answer is – these things will be discussed between the prime minister and the president, and I can’t give you a list of equipment at the moment that we would send, but the position that we’ve taken more broadly in the war, as I said, is we’ve not sought to be a protagonist in this.”

Speaking earlier to Times Radio, McFadden said: “There’s a lot of rhetoric, always, in this presidency. Underneath that, there is a good and close relationship between the United Kingdom and the United States. I’m confident that will continue. We speak to one another all the time.

“But that doesn’t mean that we will always have to support every intervention and every action that the United States chooses to take.”

Starmer has worked hard to maintain good relations with Trump as far as possible, for example using his first visit to the Trump White House to invite the president for an unprecedented second state visit to the UK.

But Trump has repeatedly criticised Starmer over what he sees as a lack of enthusiasm for supporting the attack on Iran, saying earlier this month: “This is not Winston Churchill that we’re dealing with.”

Downing Street is, however, confident that its stance of only supporting defensive measures against Iranian drone and missile attacks is in accordance with international law, and generally matches the mood of the public in the UK.

Starmer and Trump spoke by phone on Sunday. According to a Downing Street readout of the call, the pair “discussed the ongoing situation in the Middle East and the importance of reopening the strait of Hormuz to end the disruption to global shipping, which is driving up costs worldwide”.