The patrols, which began Friday, are being led by USA special operations forces, a US official told CNN.
Turkish President Tayyip Erdogan, who is set to meet U.S. President Donald Trump in Washington in mid-May for the first time, called on America to "join hands and turn Raqqa into ISIS' grave".
On Tuesday, photos published by AFP depicted U.S. officers from the US-led coalition visiting YPG fighters at the site of Turkish airstrikes near a northeastern Syrian Kurdish town (Derik in Kurdish, Al-Malikiyah in Arabic).
The YPG is a key component of the Syria Democratic Forces (SDF), a USA -backed alliance of Arab and Kurdish fighting groups involved in a campaign to drive Islamic State out of its Syria stronghold, Raqqa.
"We are seriously concerned to see USA flags in a convoy that has YPG rags on it".
Both Turkey and the USA list the PKK as a terrorist organization, but the US insists that its militia partners in Syria are a separate group from the PKK guerillas fighting Turkey.
But Ankara says the YPG is a terror outfit and the Syrian branch of the Kurdistan Workers' Party (PKK), who have waged an insurgency since 1984 inside Turkey that has left tens of thousands dead. But they will know that the Turkish military can come'.
Erdogan said: "We will be forced to continue (our offensives)".
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Police said the southbound lanes Third Street and State Route 4 will remain closed for an unknown amount of time. For those traveling south, motorists were advised to take I-75 to I-70 eastbound to I-675 south.
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Please fill out the form below with the eleven players you want to see playing for City against Boro. The Manchester Derby didn't go exactly as planned, but at least we got a point and can move on.
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Even double executions on the same day are rare - the last time it was attempted, by Oklahoma in 2014, it led to a "bloody mess". The legal issue that halted Monday's executions for Ward and Davis hinged on a separate, broader case pending before the U.S.
Footage shot Friday night showed a long line of trucks carrying military vehicles driving to the border area.
The SDF retook Manbij from IS control, and Turkey - with its troops nearby - said it won't allow the town to be under Kurdish control, threatening to move on it.
Turkey's private Ihlas news agency reported that the relocation came after Turkish officials stated that a phase of Turkey's cross-border operation in Syria had been completed.
Erdogan also told reporters that Ankara is concerned by the photos showing United States soldiers attending the funeral of YPG fighters who were killed by Turkish airstrikes in northern Syria last week. "In this attack by the Turkish army, 20 of our comrades were killed and 18 of our comrades were wounded", the YPG said.
Erdogan hinted his country is also ready to repeat its attacks in Sinjar, Iraq, to prevent it from turning into a base for the Kurdish militia.
Kurdish officials said the USA patrols are monitoring the Turkish-Syrian border to prevent an increase in tensions with Turkey, a North Atlantic Treaty Organisation member and US ally.
Also yesterday, the Syrian military said its troops and allied fighters had repelled an ISIL attack on a strategic area held by the government in a southeastern area of Aleppo province. Some footage posted online showed Kurdish residents cheering US -flagged vehicles as they drove by.
The escalation led to US patrols along the border in Syria. This concern was one of the reasons behind Ankara launching a large-scale military operation in the border region with Syria. "This is a message from the United States to Turkey to stop attacking the YPG, since they fear this could threaten the anti-ISIS Raqqa operation", he added.