US Secretary of State Antony Blinken on Friday told Turkey it was "imperative" to work against a resurgence of the Islamic State (IS) group in Syria following the fall of Bashar al-Assad.
The top US diplomat also said he saw "encouraging signs" on reaching a ceasefire in the war-torn Gaza Strip.
His remarks came on the second leg of a whirlwind regional tour following the sudden ouster of Bashar al-Assad in a lightning offensive spearheaded by Islamist-led rebels, ending five decades of repressive rule by his clan.
After visiting Jordan, he flew to Turkey on Thursday evening where he met for more than an hour with President Recep Tayyip Erdogan at Ankara airport, a US official said.
"Our country worked very hard and gave a lot over many years to ensure the elimination of the territorial caliphate of ISIS (IS), to ensure that that threat doesn't rear its head again," Blinken said on Friday morning.
"And it's imperative that we keep at those efforts."
In response, Turkey's Foreign Minister Hakan Fidan told Blinken Turkey was committed to ensuring stability in Syria "as soon as possible" and "preventing ISIS" jihadists from gaining a foothold there.
On Thursday, Erdogan assured Blinken Turkey would never ease up in the fight against IS in Syria, despite its operations against Kurdish fighters seen as key to containing the extremists.
"Turkey will never allow any weakness to arise in the fight against ISIS," Erdogan told him.
As the Islamist-led rebels marched on Damascus, Turkey and its proxies began their own offensive against the SDF (Syrian Democratic Forces), a US-backed Kurdish-led group that Blinken on Thursday said was "critical" for preventing a resurgence of IS in Syria.
The fighting between the two proxy forces has raised concern about the NATO allies' competing interests in Syria.
Blinken also said he saw "encouraging signs" of progress toward a ceasefire in the Gaza Strip, urging Turkey to use its influence to encourage Hamas to accept.
"We discussed Gaza, and we discussed I think the opportunity... to get a ceasefire in place. And what we've seen in the last couple of weeks are more encouraging signs that that is possible," Blinken said.
Blinken, who leaves office next month following Donald Trump's election victory, began his Syria tour in Jordan on Thursday on what was his 12th visit to the Middle East since the October 7, 2023 Hamas attack on Israel, which sparked the war in Gaza.
"We talked about the imperative of Hamas saying 'yes' to the agreement that's possible, to finally help bring this to an end," he said of his talks with both Erdogan and Fidan.
"And we appreciate very much the role that Turkey can play in using its voice with Hamas to try to bring this to conclusion," he added.
Turkey has long had close ties with the leadership of Hamas, viewing it as a national liberation movement rather than a proscribed terror organisation like most Western nations.
A blistering critic of Israel and its actions in Gaza, Erdogan has frequent hosted Hamas' political leadership who have used Istanbul as one of their foreign bases during his two-decade rule.
