US Secretary of State Marco Rubio on Thursday met Syria's foreign minister to discuss normalising relations after US President Donald Trump moved to ease sanctions on the war-battered country.

The top US diplomat, in the Turkish resort of Antalya for a meeting of Nato foreign ministers, opened talks with Syrian Foreign Minister Asaad al-Shaibani, a State Department official said.

The closed-door meeting also involved top Turkish officials, including Foreign Minister Hakan Fidan, the official added.

Turkey has been the major backer of Islamist guerrillas who, in December, launched a lightning offensive that ousted long-time leader Bashar al-Assad after years of stalemate.

Turkey, as well as Saudi Arabia, had been pushing for better relations with the new Syrian government and a lifting of economic pressure in place since Assad's time.

Trump, on a visit to Riyadh on Tuesday, announced that he would lift sanctions, saying that he wanted to give Syrians "a chance at greatness."

Trump, always in tune with public reaction, throughout his Gulf trip has noted how he received a standing ovation during the announcement before an investment forum.

In Riyadh, Trump met with Syria's interim president, Ahmed al-Sharaa, who was until recently on a US wanted list, calling him a "young, attractive guy."

Trump said Rubio would discuss normalisation in greater detail during the meeting with the foreign minister. (AFP)