US President Donald Trump has urged Turkey to stop buying oil from Russia, part of a wider drive to cut off Moscow's energy funding as the war in Ukraine rages on.

Speaking alongside President Recep Tayyip Erdogan at the White House, Trump said halting those imports would be the best thing his Turkish counterpart could do. The Oval Office meeting ended without any firm commitments to lift US sanctions on Turkey or sell advanced F-35 fighter jets, although Trump expressed optimism about both issues.

Turkey has for years been prevented from buying US F-35s. In 2019 it was expelled from a programme where it produced parts for the warplane after it acquired air defence systems from Russia.

During a brief question-and-answer session alongside Erdogan in the Oval Office, Trump said he would like Turkey to stop buying any oil from Russia while Russia continues its rampage against Ukraine. The best thing he could do is not buy oil and gas from Russia, Trump said. If he did that, that would be the best thing.

Trump added that he believes Erdogan is respected by both Ukrainian President Volodomyr Zelensky and Russian President Vladimir Putin, meaning that he could have a big influence on the war if he wants to. Alongside India and China, Turkey is among Moscow's biggest customers for oil and gas exports.

The US president's comments come just weeks after he indicated he would impose tougher sanctions on Russia if NATO countries met conditions that included halting imports of Russian oil. Earlier this week, during a lengthy speech at the UN General Assembly, Trump accused NATO allies of funding the war against themselves through their energy purchases from Moscow.

During Trump's first term, the US removed Turkey from the F-35 programme after it purchased S-400 surface-to-air missile systems from Russia. A 2020 US defense bill included an amendment preventing Turkey from acquiring F-35s unless it certified that it had abandoned the Russian S-400 system.

Some US lawmakers have expressed concerns about the sale due to Turkey's military actions in Syria and violations of Greek airspace, but in the Oval Office, Trump assured Erdogan that he would be successful in securing the purchases he desires. He suggested that sanctions against Turkey could be lifted very soon if negotiations went well.