Some conservative members of Donald Trump’s “Make America Great Again” movement have reacted angrily to the president’s plans to sell weapons to Nato, arguing it is a betrayal of his promise to end US involvement in foreign wars.

On Monday, Trump said he would send weapons to Ukraine via Nato, while also threatening Russia with more tariffs if a deal to end the war is not reached in 50 days.

Republican Congresswomen Marjorie Taylor Greene, a key Trump ally, and former Trump strategist Steve Bannon are among those who have criticised the decision, with Bannon telling his podcast listeners that Ukraine is a “European war”.

The White House has emphasised that Europe will pay for the US-made weapons.

In an interview with the New York Times, Greene – an isolationist member of Congress from Georgia who has been one of the most loyal Trump supporters on Capitol Hill – said the move was at odds with what she had promised voters on the campaign trail.

“It’s not just Ukraine; it’s all foreign wars in general and a lot of foreign aid,” she said. “This is what we campaigned on. This is what I promised also to my district. This is what everybody voted for. And I believe we have to maintain the course.”

Trump sought to emphasise that the weapons would be paid for rather than given as direct aid, saying on Monday: “We’re not buying it, but we will manufacture it, and they’re going to be paying for it.”

But in a rare public disagreement with the president, Greene expressed scepticism that US taxpayers would ultimately avoid bearing any cost and, in a post on social media, criticised “backdoor deals through Nato”.

“Without a shadow of a doubt, our tax dollars are being used,” she told the New York Times, arguing that indirect costs such as US training missions and contributions to Nato qualify as US involvement.

“I said it on every rally stage: no more money to Ukraine. We want peace. We just want peace for those people,” she said. “And guess what? People haven’t changed.”

One former Trump campaign official, speaking on the condition of anonymity to Politico, said Europe’s purchase of the weapons “mitigates” the anger from Trump’s isolationist supporters.

“But we still hate it,” the official said. “This is not our war, and escalation isn’t in America’s interest.”

Steve Bannon, a former adviser to Trump, said on his War Room podcast that “Ukraine is getting so dangerous”.

“It’s a European war. Let Europe deal with it,” he said. “They have the resources. They have the manpower.”

“We’re about to arm people we have literally no control over,” Bannon said of Ukraine. “This is old-fashioned, grinding war in the bloodlands of Europe – and we’re being dragged into it.”

In a statement quoted by Politico, White House Deputy Press Secretary Anna Kelly said that Trump’s MAGA base “aren’t panicans like the media”.

“They trust in Trump, and they know that this president is restoring peace through strength.”

The BBC has contacted the White House for comment.

A White House official who spoke to Politico on the condition of anonymity disagreed that the president’s base opposed his moves. They pointed to one recent poll that suggested nearly two-thirds of Trump voters support continuing to send arms to Ukraine.

Officials in the Trump administration have also defended the president’s decision, with Under Secretary of Defense Elbridge Colby writing on X that Trump’s “America First message is that our alliances have to be fair and equitable”.

“This is eminently reasonable but was treated for many years as heresy,” he added. “Yet now with the historic Nato commitment we see that it can work.”

That recent commitment from Nato leaders to ramp up defence spending to 5% of their economic output was praised by Trump supporters on Monday, who argued that even with the new weapons deal Europe was taking on more responsibility for its defence.

And in an exclusive interview with the BBC on Monday, just hours after he met Nato chief Mark Rutte at the White House, Trump said the alliance was now “paying its own bills”.

He affirmed his support for the organisation’s common defence principle, and said he was “disappointed but not done” with Russia’s Vladimir Putin.

The president said that he had thought a deal to end the war in Ukraine was on the cards with Russia four different times.