The remarks of Brett McGurk, the US special envoy for the global coalition against the Daesh (also known as ISIL or ISIS), were slammed by Huseyin Muftuoglu, spokesperson of the Turkish Foreign Ministry, as "provocative," according to a written statement from the spokesperson.
Turkish embassy in Washington would also issue a demarche regarding the issue, he added, Xinhua news agency reported.
McGurk said at a panel in the Middle East Institute in Washington on Friday that Idlib has turned into a "safe zone for al-Qaeda terrorists on the Turkish border."
A Turkish Foreign Ministry official source said on condition of anonymity that the remarks were considered implying Turkey's role for presence of al-Nusra group in Idlib.
McGurk also said at the panel that the US intended to work with Turkey to close down the northeastern border to recruited militants.
The envoy said it might not be the best approach for some partners of the US" to send tens of thousands of weapons and turn their faces to the other side as foreign fighters enter this area."
Deputy Undersecretary of the Foreign Ministry Sedat Onal asked the US envoy by phone to "correct" his statements if not aimed any provocation, said the official source.
The Turkish diplomat warned McGurk that these kinds of remarks could harm the grounds of cooperation between the US and Turkey at a time that Washington is seeking cooperation with the Turkish government for post-ISIL period in Syria, it added.
McGurk draws Turkey's ire particularly after his visits to the ranks of the People's Protection Units (YPG) in northern Syria, which Ankara views as the offshoot of the outlawed Kurdistan Workers' Party (PKK).
In May, Turkey's Foreign Minister Mevlut Cavusoglu demanded the US remove the pro-Kurdish envoy.