The UK must play peacemaker between the US and Ukraine following a fresh dispute over Washington’s agreement to buy Russian diesel, Defence Secretary Wes Streeting has said.

The rift widened after Ukraine President Volodymyr Zelensky warned that the US government's deal to secure millions of tonnes of diesel from President Vladimir Putin’s Russia would serve to prolong the conflict.

US President Donald Trump hit back and said it was "time for Ukraine to get a new president".

Elections have been suspended in Ukraine since Moscow’s incursion in 2022, with the country put under martial law.

Prime Minister Andy Burnham has reaffirmed his "complete solidarity" with the Ukrainian leader during a phone call on Saturday, with plans to meet him in person – potentially as soon as this week.

Mr Streeting said the UK could help to diffuse the tension between the two allies.

“In terms of the exchange between President Trump and President Zelensky, it is not the first time we’ve seen these sorts of tensions between Kyiv and Washington,” the cabinet minister told Sky News.

“Our approach, our role, our responsibility in this situation is to try and bring our friends back together.”

Diesel prices have soared in recent months because of the disruption to global supplies caused by the US-Israel war against Iran, and the ongoing conflict between Russia and Ukraine.

With the US electorate heading to the polls next month for the midterm elections, Mr Trump is under pressure to bring down fuel prices as he looks to persuade voters to keep his Republican party in control of Congress.

Mr Streeting said: “Let’s be candid about this: midterms are coming up, cost of living is an issue.

“No doubt President Trump is feeling the same pressure that lots of leaders are facing in terms of wanting to ease cost-of-living pressures, energy prices.”

Mr Streeting also sought to play down the effect the move has on US support for Ukraine, saying critics should not “overstate the impact”.

“We actually do a lot of procurement with and through the United States to support Ukraine with things like missile defences,” he told the BBC in another interview.

“There is clearly a big effort being led by the United States on the diplomatic track.

“So, let’s not overstate the impact of President Trump’s decision on purchasing oil from Russia, and let’s not also understate US support for Ukraine.

“What we want to see, though, is maximum unity across Ukraine’s allies and it’s in that context that we’re trying to increase economic pressure on Russia, not to give President Putin any sense of a weakening of Western resolve, which remains absolute.”

The UK has pledged to maintain pressure on Russia through tough sanctions after the move from Mr Trump.

The diesel deal comes only a month after the US leader signed a sweeping Russia sanctions law aimed at clamping down on the oil and gas revenues that fuel Moscow’s war against Ukraine.

The Prime Minister told Mr Zelensky he recognised it had been a “difficult” 24 hours for Ukraine when they spoke on Saturday.

Mr Burnham pledged the UK would take further action to “constrain the Russian war machine”.

Mr Zelensky had criticised Mr Trump’s deal, saying it “plays into Russia’s hands” and would prolong the war.

The US president, meanwhile, lashed out at the Ukrainian leader on Saturday, suggesting Mr Zelensky had not done enough to bring an end to the war with Russia.

Speaking at the White House, Mr Trump said: “I suggest they get a new leader who can make a deal″, adding that “for some reason (Zelensky) never does”.

He added: “I think it’s time for Ukraine to get a new president.”