U.S. President Joe Biden told Turkey's President Tayyip Erdogan his request for F-16 fighter jets had to go through a process in the United States and expressed a desire to handle disagreements between the two countries effectively.

Biden also raised the issue of human rights during their meeting on the sidelines of the G20 in Rome, a U.S. senior administration official told reporters.

The leaders met amid tensions between the two countries over defense and human rights issues.

A different U.S. administration official said on Saturday that Biden would warn his Turkish counterpart that any "precipitous" actions would not benefit U.S.-Turkish relations and that crises should be avoided after Erdogan threatened to throw out the U.S. ambassador to Turkey and other foreign envoys for seeking the release of jailed philanthropist Osman Kavala. 

Erdogan later withdrew his threat to expel the envoys.

"President Biden reaffirmed our defense partnership and Turkey's importance as a NATO Ally, but noted U.S. concerns over Turkey’s possession of the Russian S-400 missile system," the White House said in a statement after the meeting.

"He also emphasized the importance of strong democratic institutions, respect for human rights, and the rule of law for peace and prosperity," it said.

The two men discussed Turkey's request to purchase F-16 fighter jets, which U.S. lawmakers have opposed on the grounds that Turkey purchased Russian missile defence systems.

"The president took on board his ... desire to have them but made very clear that there is a process that we have to go through in the U.S. and committed to continuing to ... work through that process," the senior administration official said.

Biden and Erdogan posed for photos before their talks on Sunday. Asked if he planned to give Turkey F-16s, Biden said they were "planning to have a good conversation."