Turkey on Monday dropped its refusal to allow Kurdish fighters over the border to defend the besieged Syrian town of Kobane, saying it was now helping Iraqi peshmerga to cross the frontier in a major policy shift.
Foreign Minister Mevlut Cavusoglu said Turkey had no desire so see Kobane fall to Islamic State (IS) jihadists who have been battling Syrian Kurdish fighters for over a month for control of the town.
The influx of the well-trained peshmerga fighters into Kobane could be a major boost for the Kurds, who are now being helped by US-led air strikes and air drops.
"We are assisting peshmerga forces to cross into Kobane," Cavusoglu told reporters in Ankara. "We have no wish at all to see Kobane fall" to the jihadists.
The Kurdish Rudaw news agency reported that Turkey had approved the request from Massoud Barzani, the president of the Iraqi Kurdistan region, for the peshmerga fighters to cross.
The switch came after the American military dropped weapons, ammunition and medical supplies to the Syrian Kurdish fighters from cargo aircraft.
Cavusoglu did not comment directly on the air drops, saying only that Turkey was now "evaluating" the latest US move.
"We have been in full cooperation with the coalition. We want to be rid of all the threats in the region," he said.
NTV television quoted sources as saying the transit of fighters was already in progress and would continue. It was not clear where they were crossing the border.
Turkey has until now refused to allow Kurdish fighters to cross its border to join the battle against IS militants for Kobane, fearing the creation of a powerful Kurdish fighting force straddling the border.
Turkish security forces have been waging a 30-year conflict with the fighters of the Kurdistan Workers' Party (PKK), whose battle for self-rule in the southeast has left 40,000 people dead.
However Turkey in recent years has built up strong relations with the Kurdish authorities in the Kurdistan region of Iraq which control the peshmerga forces.
Despite the agreement over the peshmerga, Turkey is still set to block any PKK fighters from entering Syria.
President Recep Tayyip Erdogan at the weekend rejected calls for Turkey to arm the main Kurdish party in Syria, the Democratic Union Party (PYD), saying "just as the PKK... it's a terrorist organisation."
Sinan Ulgen, head of the Istanbul Centre for Economics and Foreign Policy Studies (EDAM), said the developments showed there was agreement between Washington and Ankara on helping Kobane.
He said Turkey was playing a "double game" between Erdogan's tough rhetoric and its desire not to let Kobane fall and thus ruin Turkey's own peace process with the Kurds.
"By letting just the peshmerga into Kobane, the Turkish leaders can say they are not helping the PKK and can reassure the nationalist wing of the country," he told AFP.
Cavusoglu reiterated that Turkey would not give support to the PYD, saying that "like IS, the PYD wants to control a certain region of Syria" and therefore posed a threat to Syria's future.
"The PYD and other groups affiliated with it need to change their policies in Syria and give up these ambitions," he said.
Turkey has long made no secret of its animosity towards the PYD for seeking to create a Kurdish region in northern Syria and refusing to show sufficient hostility to President Bashar al-Assad.
Turkey has come under increasing pressure over the last month to step up its support for the international coalition fighting the jihadists.
But Ankara has so far refused to use its own troops or even let US forces launch their bombing raids on IS from the Incirlik air base.
Turkish television, citing foreign ministry sources, said Turkish air space had not been used for the US air drops.
Erdogan wants the United States to commit to implementing a security zone inside Syria and create a strategy for bringing down Assad before Turkey plays a full role in the coalition.