But it's no longer the nerve center for the Islamic State's mission of carnage.
The U.S. military said in a statement emailed to journalists that the force would be "internally focused".
More immediate, Tillerson called for Russian Federation to continue working with the USA on a "de-escalation" area in southwest Syria and stick to commitments to a United Nations -led peace process. "We are helping our brothers there so that they can protect their own territories", said Erdogan, stressing that the Turkish army would "destroy" all terror spots in Syria one by one, starting with the Afrin and Manbij regions. Their deployment as a border security presence makes just as much sense.
Tillerson praised Turkey's role in taking on Islamic State.
The United States over the weekend announced plans to create a 30,000-strong internal security and border security force, half of which would be SDF fighters.
The force will be essentially a restructured version of the Syrian Democratic Forces, or S.D.F., its spokesman, Mostafa Bali, said Tuesday.
Tillerson had also said the USA would continue to work with Turkey and consider Ankara's concerns about the PKK. It has criticized the USA for extending support and arming the Kurdish forces as part of the campaign that drove the Islamic State militant group from large parts of Syria. Tanks amassed near the border with Syria, while Turkish media reported that medical personnel in Kilis, a Turkish town across the border from Afrin, were asked not to take leave, apparently in anticipation of military operations. Saying that the force would represent "an army of terrorists", Turkish President Recep Tayyip Erdogan has vowed to wage war on Syria's Kurds.
"Continued strategic threats to the USA from not just ISIS and al Qaeda persist, and this threat I am referring to principally is Iran", Tillerson said, adding, "In short, Syria remains a source of severe strategic threats".
The United States now has about 2,000 troops in Syria as part of the war against the ISIS, which has been decimated in both Syria and Iraq by the US and its allies on the ground, including Syrian Kurds. Nevertheless, the Trump administration should stand its ground. The militant group's top leaders are believed to be hiding there. "Regardless of who backs them; whether it is the USA or other countries, it doesn't matter to us".
Free Syrian Army envoys have urged US officials at talks in Washington to resume a suspended Central Intelligence Agency program of military aid if it is serious about challenging growing Iranian influence in Syria, according to Syrian opposition figures.
Syria has been locked in a vicious civil war since early 2011 when the Bashar al-Assad regime cracked down on pro-democracy protests with unexpected ferocity.
The move has enraged Russia, Iran, the Syrian regime, and especially Turkey. Each country has been hit hard by Islamic State terror attacks.
Speaking in a major Syria-policy address hosted at Stanford University by the Hoover Institution, Tillerson listed vanquishing al-Qaida, ousting Iran and securing a peace settlement that excludes President Bashar Assad as among the goals of a continued presence in Syria of about 2,000 American troops now deployed in a Kurdish-controlled corner of northeastern Syria.
Additionally on Tuesday, Erdogan called on the North Atlantic Treaty Organization (NATO) to take a stance against the United States over its Syria border force plan.