ANKARA (Reuters) - U.S. Secretary of State Rex Tillerson acknowledged on Thursday that Washington faced difficult choices in the fight against Islamic State in Syria but sought to downplay differences with NATO ally Turkey over support for Kurdish militia fighters.

Speaking after meetings in Ankara with Turkish President Tayyip Erdogan and senior government ministers, Tillerson said there was “no space” between Turkey and the United States in their determination to defeat Islamic State.

Erdogan and his government have been incensed by U.S. support for the Syrian Kurdish YPG militia, seen by the Pentagon as a reliable partner but by Turkey as a hostile force with deep links to Kurdish PKK militants who have waged a three-decade insurgency against the Turkish state.

It is particularly frustrated by the use of YPG fighters in a planned U.S.-led offensive to retake Islamic State’s Syrian stronghold of Raqqa, an operation in which Ankara has long said it wants to play a role.

“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 told a joint news conference with Turkish Foreign Minister Mevlut Cavusoglu.

Cavusoglu said Washington accepted there was no difference between the YPG militia and the PKK. Tillerson condemned recent PKK attacks in Turkey but made no such acknowledgement.

He said his talks focused on the creation of “stabilization zones” in Syria so refugees could return home and that a number of options on how to secure such areas were being explored.

Turkey, sheltering more than 2 million Syrians, has long called for such safe areas but the idea has gained little traction among Western allies who question how such zones can be carved out without a significant foreign military presence.

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STRAINED TIES

Tillerson’s visit comes at a difficult time in U.S.-Turkish relations. Ties soured under former U.S. President Barack Obama and officials in Ankara have been hoping for a reset under Donald Trump, but there have been few signs of improvement.

Aside from differences over Syria, relations have also been strained by the continued presence in the United States of Turkish cleric Fethullah Gulen, blamed by Erdogan for a failed coup last July and whom Ankara wants extradited.

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Cavusoglu said Turkey expects Washington to take concrete steps on Gulen’s extradition, including his temporary detention. U.S. officials have in the past said that is a matter for the U.S. judicial system.

Tillerson's trip was further clouded by the arrest in New York on Monday of an executive of Turkey's state-run Halkbank HALKB.IS, who is accused of conspiring with Turkish-Iranian gold trader Reza Zarrab in a multi-year scheme to evade U.S. sanctions on Iran.

Cavusoglu described the arrest of the banker as a “political” move and said the U.S. attorney who launched the case against Zarrab had close ties with Gulen’s supporters.

Tillerson’s visit comes less than three weeks ahead of a referendum at which Erdogan is seeking constitutional change to boost his powers, a move which his opponents and some European allies fear will bring increasing authoritarianism.

Tillerson did not meet members of the Turkish opposition during his visit, apparently avoiding domestic issues while trying to keep the focus on the fight against Islamic State.

It was a change in tone from U.S. visits under Obama. Then Vice President Joe Biden said during a Jan. 2016 visit that Turkey was setting a poor example for the region by intimidating the media and curtailing internet freedoms.