US Secretary of State Rex Tillerson says the fate of President Bashar al-Assad is up to the Syrian people to decide.
"I think the longer term status of President Assad will be decided by the Syrian people," Tillerson told a joint press conference with Turkish Foreign Minister Mevlut Cavusoglu in Ankara on Thursday.
The remarks are a significant departure from the position of the former US government, which made any resolution of the Syria crisis conditional on President Assad stepping down.
As for Turkey, the country has been a staunch supporter of a campaign pushed by Saudi Arabia and Qatar to oust Assad, but it has moderated that stance since warming relations with Russia, which is a key ally of the Syrian government.
Meanwhile, Ankara and Washington have run into great difficulties over the presence of Kurdish militants near Turkey's border with Syria. The US sees the militants as an ally in the region, but Turkey says they are linked to the militants of the Kurdistan Workers' Party (PKK).
On Thursday, Tillerson sought to play down the differences, saying that there was "no space" between Turkey and the US in what he described as their resolve to defeat Daesh.
The two countries have been at odds over whether to include Kurdish forces in an operation to retake the city of Raqqah, which is the main stronghold of Daesh in Syria.
Tillerson said he and Turkish leaders were still exploring "a number of options and alternatives" for retaking Raqqah.
His talks with Turkish leaders focused on the creation of stabilization zones in areas cleared of Daesh in Syria and a number of options on how to secure such areas were explored.
On Syria, the top US diplomat said tough choices should be made regarding the crisis.
“What we discussed today are options that are available to us. They are difficult options. Let me be very frank, it's not easy, they are difficult choices that have to be made," Tillerson said.
Turkey dismayed by US support for Syria Kurds
For his part, Cavusoglu said US support for Kurdish forces in Syria had saddened Turkey and affected bilateral ties.
He also warned that any US backing for the Kurdish People's Protection Units (YPG) would mean a risk for Syria's future.
"It is not good or realistic to work with a terror group while fighting another terror group,” the Turkish foreign minister said.
Ankara also expects Washington to take concrete steps on the extradition of US-based opposition cleric, Fethullah Gulen, who is blamed for the abortive military coup in Turkey last summer, Cavusoglu added.
Tillerson meets Erdogan, Yildirim
Earlier on Thursday, the US top diplomat sat down with Turkish President Recep Tayyip Erdogan.
Sources in Erdogan's office said that during the meeting, the Turkish president had stressed the importance of working with "right and legitimate" actors in the fight against terrorism.
Erdogan also reiterated Turkey’s call for Gulen’s extradition, according to the sources.
Tillerson later met with Turkish Prime Minister Binali Yildirim, discussing Gulen’s extradition among other issues, according to a short statement issued by Turkey’s Prime Ministry.
Tillerson's visit to Turkey came one day after Yildirim announced the end of the country's 'Operation Euphrates Shield' on the Syrian soil, which had been condemned by Damascus as an act of aggression.
Turks protest Tillerson's visit
As Tillerson held talks, people held a protest outside the American consulate in Istanbul to voice their opposition to the visit.
Demonstrators chanted slogans and held signs reading, "Damn American imperialism, you cannot separate our country.”