(Updates with statements from Pentagon spokesman and Turkey's U.N. envoy)

Turkey has informed NATO of its plans for a cross-border operation into Syria’s northwestern province of Idlib and has requested for the alliance to enforce a no fly zone over the region ahead of the offensive, the Independent Turkish reported on Wednesday.

Turkey announced on Wednesday that it had completed preparations to implement its own operation plan regarding the last rebel-held region in Syria, where the Syrian government, backed by Russian forces, have intensified an attack on rebel forces since last month.

“We will end the aggression of the regime in Idlib,” Turkish President Erdoğan told his parliamentary party on Wednesday, referring to the Syrian President Bashar Assad’s government in Damascus.

“These are the last days for the regime to withdraw, we are giving our last warnings,” he added.

Turkey’s U.N. envoy Feridun Sinirlioğlu echoed Erdoğan’s statements during a U.N. Security Council meeting in New York on Wednesday, saying Ankara would not abandon its observation posts in Syria and government forces in the country must withdraw from the region.

Turkey will strike at all targets that pose a threat in İdlib, state-run Anadolu news agency quoted Sinirlioğlu as saying.

Ankara has demanded for Syrian troops in Idlib to withdraw by the end of February from areas where Turkey maintains observation posts built under a 2018 deal made with Russia to prevent an attack by Damascus on the province.

Thirteen Turkish soldiers were killed this month by Syrian shelling and almost one million people have flocked to areas near the Turkish border, fleeing the Syrian government advance on the country’s last major rebel-held enclave.

Pentagon spokesman Jonathan Hoffman said the United States believed Russia and Turkey were "very close" to a more extensive conflict.

"We are seeing the Russians and the Turks have come very close to having more extensive conflict in the area," Hoffman told reporters at a Wednesday press briefing, calling on the international community to take measures to stop the Syrian government's advance on Idlib.

A diplomatic source from a NATO country told Russian news agency TASS on Monday that the alliance had no plans to provide Ankara with military support if Turkey launches a military operation in northern Syria.

"NATO countries will not support the invocation of Article 5 over the death of Turkish troops in Idlib in early February," the source said.