US President Donald Trump is facing a growing backlash over plans to import diesel from Russia as the Iran war continues to impact global energy prices.

Trump on Friday announced that Russian President Vladimir Putin had agreed to release 300,000 tonnes of diesel immediately "to the American and global marketplace" followed by several other shipments.

That is despite signing legislation to authorise fresh US sanctions and tariffs on nations that import Russian oil and gas just weeks ago.

The move has been criticised by some Republican and Democratic lawmakers, who believe the deal violates US laws.

In addition to the initial release of 300,000 tonnes of diesel, Trump said Russia would then supply 500,000 tonnes in November and another million after that.

This would be followed by a further three million tonnes, to be delivered "within a short period", depending on the condition of its refineries, which have been attacked by Ukraine during the ongoing war between the two countries.

"Lower prices for Americans, especially our Great Farmers, Ranchers, and Truckers, is my Greatest Priority," Trump wrote in a Truth Social post.

Russia's Deputy Prime Minister Alexander Novak confirmed these figures to Tass, the country's state-owned news agency, saying the export volume could reach 3 million tonnes per month in the future.

Ukrainian President Volodymyr Zelensky has called the deal a gift to Putin, amounting to "an investment in a war that must be ended".

It is understood that the US Treasury is suspending sanctions on Russian diesel exports until 7 April as part of the deal, but other assets, such as those held in American banks, remain frozen.

A group of seven senators - four Republicans and three Democrats – on Sunday said the deal violated US laws, urging Trump to "reverse course".

"The United States should not provide Putin with a financial lifeline while Russia continues to kill Ukrainian civilians," the lawmakers said.

They added that Congress had "explicitly banned Russian energy imports in 2022 to prevent American dollars from financing Putin's brutal war against Ukraine".

The statement was signed by Republicans Susan Collins, Lisa Murkowski, Thom Tillis and John Curtis, as well as Democrats Jeanne Shaheen, Richard Blumenthal and Ron Wyden.

Not everyone is opposed to the deal. Republican Thomas Massie, who has sparred with Trump a number of issues, said the US should lift sanctions on all petroleum products.

Trump's Treasury Secretary Scott Bessent told Fox News the agreement would work through existing legal channels the US has to help bring prices down and that anyone in Congress who said it would not was wrong.

Global fuel prices have soared since the US-Israel war with Iran began at the end of February, with the fighting severely disrupting supplies of crude oil - a key ingredient in petrol and diesel.

The rising prices have become a key issue for Americans ahead of next month's midterms elections, which will determine if Trump's Republican Party maintains control of Congress.

Polls show a majority of Americans disapprove of his handling of the economy and the war in Iran and he has been searching for ways to ease his party's political pain.

The toll the war is taking has been acutely felt by US agricultural states, which rely heavily on diesel to operate farming machinery and to transport their products to market.

The average diesel price in the US is currently $6.28 (£4.74) a gallon, according to the AAA, down from the record high of $6.53 recorded at the end of September.

Analysts have questioned whether Russia is capable of providing that quantity of diesel and the extent to which doing so will ease prices for American consumers.

The US uses approximately 3.6 million barrels of diesel a day, so even if Russia delivers its promised 300,000 tons this month, that would amount to approximately half of the US's daily consumption.

It is not only at home that Trump is facing opposition to his diesel deal with Russia. A number of international leaders have criticised it, including Canadian Prime Minister Mark Carney and UK Defence Secretary Wes Streeting, who said the US and other allies of Ukraine should focus on ramping up pressure on Russia to end the war.

Meanwhile, Trump announced in Sunday that Russia and Ukraine had reached an "energy ceasefire" but did not give more details. Ukrainian President Volodymyr Zelensky welcomed this, but Moscow did not respond.