A White House official says the United States thinks it is "extremely unlikely" Turkey used chemical weapons against the Kurds. "After the people's protection Units leave it, we together with the United States can take joint steps based on trust", said Cavusoglu.
"There are significant issues that the secretary of state and his foreign minister counterpart agreed that we would work through", he said.
Turkey has long protested against the U.S.'s partnership with the People's Protection Units (YPG), a Syrian Kurdish group linked to the Kurdistan Workers' Party (PKK), in the anti-Islamic State of Iraq and the Levant (ISIL) coalition.
Turkey launched an air and ground offensive last month on Syria's Afrin region, opening a new front in the multi-sided Syrian war to target Kurdish fighters in the autonomous canton in the north.
Kurdish forces in Syria and the Syrian Observatory for Human Rights have reported a suspected gas attack in the country carried out by Turkish forces Friday.
Tillerson's visit is part of a flurry of high-level meetings between top USA and Turkish officials in recent days. We're going to lock arms.
The alleged use of chemical weapons in the seven-year civil war in Syria has always been an issue, with the United Nations previously declaring evidence of use by President Bashar al-Assad in his fight against rebels.
Ankara has placed greater emphasis in recent months on the need to combat the Kurdish militia and has said the United States is merely using one terrorist group to combat another. The mainly Arab city is separated from Afrin by an enclave captured from IS by pro-Turkish rebels in a Turkish-led operation in 2016.
The latest development coincided Friday with a Syrian regime decision to allow Kurds demonstrate in Damascus against the Turkish military operation in northern Syria, carrying portraits of Abdullah Ocalan, imprisoned leader of the PKK.
Hedu further noted that Turkish troops actually did not advance in Afrin, but engaged in hit-and-run tactics instead.
From the beginning of Turkey's counter-terrorist operation in Afrin, "We saw suppression from the PYD/PKK terrorist organization", Abdullah said, adding: "We refused to fight, and fled Jindires".
Turkey has said it could expand its assault to those areas and last week renewed its demands for the YPG to pull out of all parts of Syria west of the Euphrates.