Finland's Prime Minister Petteri Orpo has said that US President Donald Trump's recently announced agreement for Russia to release large amounts of diesel onto world markets was a "huge disappointment".

Orpo told reporters on Tuesday that a "direct deal with Putin" was "against everything we have done together and together with the United States through the coalition of the willing and in supporting Ukraine."

He added that such a deal "funds Putin's war" against Ukraine.

The Finnish prime minister urged Europe and Ukraine's supporters to "say this forcefully to Trump".

"Continuing support for Ukraine is now more essential than ever," he added.

Trump announced on Friday that he had spoken to Russian President Vladimir Putin and they had struck an agreement for Russia to release large amounts of diesel onto world markets, a bid to lower prices that have spiked since the US leader launched the war on Iran on February 28.

Trump's decision has been met with sharp criticism across European countries backing Ukraine.

Following Trump's announcement, Britain and Germany on Tuesday pressed for more sanctions on Moscow, after the European Union on Monday formally added nearly 1,600 new Russian individuals and entities to its sanctions blacklist.