Washington DC - US President Donald Trump on Monday touted himself as a mediator between Israel and Turkey in their struggle over politically fragile Syria, where both countries are jostling for influence.

Trump, speaking alongside key ally Israeli Prime Minister Benjamin Netanyahu at the White House, touted his "great relations" with Turkish leader Recep Tayyip Erdogan as an avenue for negotiations.

"I told the prime minister, I said, just Bibi if you have a problem with Turkey, I really think I'm going to be able to work it out," Trump told reporters, using Netanyahu's nickname.

"You know, I have a very, very good relationship with Turkey and with their leader, and I think we'll be able to work it out," he added.

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Turkey is a key backer of the Islamist-led coalition in Syria that toppled Bashar al-Assad in December after almost 14 years of civil war.

Its influence on Syria's new authorities has worried Israel, which has carried out strikes and ground incursions into southern Syria to repel the government's forces from the border.

Trump appeared to acknowledge Turkey's dominance in Syria, saying he told Erdogan he had "taken it over through surrogates."

"I said, 'Congratulations, you've done what nobody's been able to do in 2,000 years. You've taken over Syria.' With different names, but same thing," Trump said.

Netanyahu, who was visiting Washington, meanwhile voiced Israeli concerns over Turkish influence in Syria while touting the US president as a mediator.

"We've had neighborly relations with Turkey that have deteriorated, and we don't want to see Syria being used by anyone, including Turkey, as a base for attack in Israel," he said.

"We discussed how we can avoid this conflict in a variety of ways, and I think we can't have a better interlocutor than the president of the United States for this purpose," Netanyahu added.