Islamic State group: Turkey and US 'ready to invade capital'
Turkey's President Recep Tayyip Erdogan has suggested he and the US are ready to drive so-called Islamic State (IS) from its Syrian stronghold of Raqqa.
Mr Erdogan said US President Barack Obama floated the idea of joint action against the militants when they met at the G20 summit in China.
He said Turkey would have "no problem" with such action.
Last month Turkey launched an operation inside Syria, targeting both IS and Kurdish rebels.
The US State Department would not confirm the details of Mr Erdogan's statement, but an official said it was important that "local forces" were involved in the fight to deliver "a lasting defeat" to IS.
"The actions that Turkey is currently taking along its border with Syria, with US support, is having the important effect of isolating Raqqa," the official said.
"That is a critical step in our ultimate objective to liberate Raqqa from Isil (IS) control."
Turkish-backed militia have driven IS from the border town of Jarablus, but Turkey has also been concerned with checking the advance of Kurdish forces whom it regards as terrorists.
The offensive continues, and Deputy Prime Minister Nurettin Canikli said Turkish forces might push deeper into Syria after securing a stretch of land along the border.
Mr Canikli also said 110 Islamic State and Kurdish militia fighters had been killed since the operation began.
Russia, which is allied to Syrian President Bashar al-Assad, said it was "deeply concerned" by the Turkish advance.
'What is necessary will be done'
Mr Erdogan's comments on Raqqa were published in Turkish media.
"Obama wants to do some things jointly concerning Raqqa," Mr Erdogan said. "We said this would not be a problem from our perspective.''
"I said: 'Our soldiers should come together and discuss, then what is necessary will be done'," Mr Erdogan added.
Mr Erdogan gave few other details but said more discussions would follow.
Raqqa's fall was a key point in the rise of IS as it seized swathes of territory in Iraq and Syria, and is now considered the jihadists' de facto capital.
Between 250,000-500,000 people are still thought to live there, with brutal stories emerging of the treatment of civilians.
Analysis: By Jonathan Marcus, BBC defence & diplomatic correspondent
Through its large-scale incursion into northern Syria, Turkey has made itself a military player in the country.
But Ankara's move, directed in part against Kurdish forces backed by Washington, prompted serious strains in US-Turkey relations, already poor in the wake of the failed coup against the Erdogan government.
There is now a desire on both sides to improve ties and the suggestion from President Erdogan of US acquiescence in a Turkish role in the wider battle-plan to recapture Raqqa from IS is clearly part of this.
It would be an acknowledgement by Washington of Turkey's continuing strategic interest in Syria.
No details have been given as to what a Turkish role might amount to but clearly if Raqqa is attacked then the zone approaching the Turkish border to the north of the city needs to be secured to block the withdrawal of fleeing IS forces.