The Turkish military operation in northern Syria called "Euphrates Shield" has ended, Prime Minister Binali Yildirim announced on Wednesday following a meeting of the National Security Council (MGK).
Also hanging over Tillerson's trip was Turkey's demand for the U.S.to extradite Fethullah Gulen, the cleric Turkey blames for instigating last year's failed coup.
The U.S. has been trying to balance its reliance on Turkey in the fight against ISIS with its support for Kurdish fighters in northern Syria - which infuriates Turkey.
Earlier in March, the USA deployed 200 more Marines to northern Syria (the outskirts of Manbij), bringing the number of US boots on the ground to more than 700. Also, it is likely that Washington wanted to discuss the impending offensive on Raqqa, the capital of the IS caliphate in Syria.
On Thursday, Tillerson sought to play down the differences, saying that there was "no space" between Turkey and the U.S. in what he described as their resolve to defeat Daesh. But Washington has been backing Syrian Kurdish fighters who have proven the most effective ground force against ISIL.
-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. Tillerson says the two countries have to continue discussing the way forward and that the options are hard. "These are not easy decisions", Tillerson said at a joint news conference Thursday in Ankara with his Turkish counterpart, Mevlut Cavusoglu.
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The only person he named was President Trump's son-in-law Jared Kushner, but his hearing has not been scheduled yet. He added that, preliminarily, he has not seen evidence of surveillance violations by intelligence officials.
Speaking after talks in Ankara, he added there was "no space" between Turkey and the U.S. over fighting the so-called Islamic State group - even as his Turkish counterpart reiterated a key point of discord.
Cavusoglu claimed the Trump administration and the USA military have accepted that the YPG - the dominant force in the US-backed Syrian Democratic Forces - is intrinsically linked to the PKK, or Kurdistan Workers' Party.
"As our justice minister and Mr. Tillerson told us, the documents are [still being] examined in detail", he said. Life is back to normal. He said he personally met with Attorney General Jeff Sessions and that it was a "good meeting".
But President Trump's former National Security Adviser Michael Flynn was reported on Saturday to have discussed removing Mr Gulen from the United States, using removal methods that went beyond the legal extradition process. "But it also means that the Turkish military will not, in all likelihood, take part in further operations other than defending the current territory of Euphrates Shield", he told AFP, of the Turkish announcement.
Turkey said it is interested in supporting the operation to take the IS stronghold of Raqqa, but not if the Kurdish militia is involved, AP reports.
But despite Mr Cavusoglu's optimism, there have been no signs yet that the USA under president Donald Trump intends to ditch the YPG as the battle for ISIL's capital of Raqqa looms.