Turkish presidential spokesman on Thursday said the possibility of formation of a PKK state on Turkish- Syrian border is out of question.

"Thanks to skillful leadership of our president, a PKK state, which was tried to be established on Turkish-Syrian border, is out of question now," Ibrahim Kalin said after a Cabinet meeting in capital Ankara.

In its more than 30-year terror campaign against Turkey, the PKK -- listed as a terrorist organization by Turkey, the U.S. and the EU -- has been responsible for the deaths of nearly 40,000 people, including women and children. The PYD/YPG is its Syrian branch, and also works under the label of the SDF.

Kalin said the Bashar al-Assad regime in Syria is carrying out attacks to provoke Turkey and take lands.

"Our related units are authorized to stop these attacks and contacts were established especially with Russia [in this regard]. The talks are going on," he added.

Earlier, Turkish Defense Ministry said in a statement the regime attacked a Turkish observation point in Syria’s Idlib province which left three Turkish soldiers wounded.

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.

Since then, hundreds of thousands of people have been killed and more than 10 million others displaced, according to UN officials.

Speaking about the U.S. acting defense secretary’s letter to Turkey's defense chief, Kalin said the letter is "against the spirit of alliance" and an "appropriate" response will be given.

The presidential spokesman said he has discussed the letter with U.S. National Security Adviser John Bolton.

The letter sent last week said that Washington was cutting short a F-35 fighter jet training program for Turkish pilots over "safety concerns."

Kalin said the U.S.’s attitude on Ankara’s purchase of Russian S-400 air missile system “would permanently harm bilateral relations” and expressed hope that the U.S. would give up this attitude.

"The F-35s, which are Turkey's right, will definitely come to our country," he added.

Delaying this process and trying to distract it with different reasons will "only" harm the process and the bilateral relations, Kalin added. 

Washington claims the S-400 purchase will jeopardize Turkey's role in the F-35 fighter jet program and has threatened sanctions.

Turkey has said there is no conflict between the S-400 and the F-35 and has called for a working group to clarify the issue