Foreign Secretary Lord Cameron warned against the “appeasement” of Vladimir Putin as he stepped up calls for the US to release billions of dollars of extra funding for Ukraine.

In a message aimed at Donald Trump and his Republican allies, the former prime minister said the stalled funding package would be good for US security and jobs and show the West was prepared to stand up against “bullies”.

Lord Cameron, who met presidential candidate Mr Trump for private talks during his trip to the US, insisted the only way to end the conflict was by backing Ukraine rather than allowing Russia to keep the territory it has occupied.

Mr Trump, who hopes to return to the White House following November’s US election, is reportedly ready to pressure Ukraine to cede Crimea and the Donbas border region as a price for peace with Russia.

But Lord Cameron told CNN during his visit to Washington: “Everyone wants to see an end to the killing and an end to the war. But you only get that by backing Ukraine, by showing strength.

“Peace comes through strength, not through appeasement and weakness.”

Asked about the reported Trump peace plan, he said: “I don’t think we should be discussing those things right now, we should be discussing how do we get Ukraine back on the front foot.

“They’ve showed incredible bravery. They’ve showed that they can win against Putin, they’re not going to lose for lack of morale, they’re not going to lose for lack of ingenuity on the battlefield.

“The only way they can lose is if we don’t give them the support they deserve.”

He added that Europe was doing more to fund its own defence – a key demand of Mr Trump during his tenure in the White House – and “Europe and America sticking together and standing up against bullies and dictators, that’s good for both of us”.

A vote in Congress on the Ukraine funding package has been held up by political wrangling, with House speaker Mike Johnson’s own position in jeopardy in the face of opposition from the Republican right.

Lord Cameron had hoped to discuss the situation with Mr Johnson, who has to decide when to put the Ukraine package to a vote, but he has failed to secure a meeting.

With Mr Trump seeking a return to the White House, Lord Cameron suggested decisions on Ukraine could not be allowed to be pushed back until after the election.

“There’s a risk that Ukraine will lose more ground to Putin, and no one wants to be in a situation in November, where we could have acted, we could have helped, we could have beaten back Putin, we could have started the process of getting a Ukraine win and getting a just peace but we failed to do that.”

Lord Cameron urged Republican politicians not to be taken in by propaganda from Vladimir Putin’s Russia.

Senior figures including House intelligence committee chairman Mike Turner and foreign affairs committee chairman Michael McCaul have warned that some of their fellow Republicans are being influenced by Russian propaganda.

Asked about the situation, Lord Cameron told MSNBC: “Don’t listen to Putin’s lies about Ukraine. It is a free democracy that wants to be an independent sovereign country, that wants to be our ally and our friend.

“And we should be standing by our friends, because the world will be watching if we don’t.”