ISTANBUL, Jan. 19 (Xinhua) -- As Turkey has been increasing its military buildup on the border threatening to clear

An operation against Afrin would mean occupation as far as international law is concerned if Turkish troops enter Syria without getting the consent of Damascus first, Huseyin Bagci, a professor of international relations, told Xinhua.

An operation against Afrin seems imminent, as Turkey, Russia and Iran have joined the chorus of opposition to a new U.S. plan to form a 30,000-strong border security force to be dominated by Syrian militia known as the People's Protection Units (YPG), with Erdogan vowing to "nip this terror army in the bud."

On Wednesday, U.S. Secretary of State Rex Tillerson denied that Washington intended to establish a border security force in Syria, claiming the issue had been "misportrayed" and "misdescribed." The next day, Turkish Foreign Minister Mevlut Cavusoglu declared on TV that Turkey's possible Afrin operation comes in response to the YPG's threat.

Ankara treats the YPG as the Syrian offshoot of the Kurdistan Workers' Party, which has been fighting against the Turkish state for more than 30 years.

Noting Turkish troops would be designated as an occupying force if they remain in Afrin after the operation, Bagci said that "the Arab League in the first place and the UN would oppose Turkey, which then would find itself in a situation very difficult to cope with."

As Turkish troops stationed on the border continue to pound YPG positions in Afrin, Turkish Chief of General Staff Hulusi Akar flew on Thursday to Moscow for a meeting with his Russian counterpart Valery Gerasimov along with Hakan Fidan, head of Turkey's intelligence agency.

As a staunch supporter of Damascus in the Syrian war, Russia has some troops in Afrin and has stood by the YPG in the past year, deterring any Turkish intervention.

Russia is known to be unwilling to totally leave the Kurdish card into the hand of the United States, the leading patron of the YPG.

Turkey may be accused of occupation, causing instability and triggering an eventual disintegration of Syria if it attacks the YPG, cautioned Cahit Armagan Dilek, a former staff officer in the Turkish military.

In his view, the YPG is seen by the world as an actor that fought to defeat the Islamic State in Syria.

Last month, Syrian Foreign Minister Walid al-Moualem accused Ankara of having conspiracy on Syria's territory, and Damascus sees the presence of Turkish troops on Syrian soil as occupation.

The Turkish military has kept under its control an area between the Afrin canton in northwestern Syria and two other YPG-held cantons on the eastern part of the Euphrates River since the end of 2016.

Jawad Abu Hatab, head of the so-called Syria's interim government, was quoted as saying last month that their main objective was to keep the areas captured by Turkish troops and guard against the Syrian government and terror groups.

Ankara perceives the YPG-held cantons, in particular the one in Afrin which is closer to the Mediterranean Sea, as a major national security threat.

Like many in Turkey, Dilek, who currently heads the Ankara-based 21st Century Turkey Institute, feels Turkey has the right to eliminate a terrorism threat from its border.

He is concerned, however, that Turkish troops may overstay in Syria, exposing Ankara to accusations of trying to occupy and dismember the neighboring country.

Ankara said it respects Syrian territorial integrity, but it is widely argued that Turkey's effort to create a Sunni-dominated area would lead to a federal Syria, given Russian and the U.S. support for Kurdish autonomy.

A federal Syria risks setting the stage for the country's eventual disintegration, which in turn would pose a major threat to Turkey's territorial integrity, as many have warned.

Turkey said it will not only clear the YPG in Afrin, but also in Manbij and in the two Kurdish cantons along the Turkish border to the east of the Euphrates.

General Akar was in Brussels on Tuesday for a NATO meeting, where he met with his U.S. counterpart Joseph Dunford. On the same day, Washington said Afrin was not within its area of operations in Syria, signaling that it would not oppose a Turkish intervention.

Dilek feels the United States may prefer to keep Ankara busy with Afrin while it is trying to build a Kurdish state on the eastern part of the Euphrates.

Many agree that intervention into Afrin without getting Russia's consent would mean trouble for Turkey.

Speaking on CNNTurk on Thursday, Cavusoglu said, "we are talking with Russians and Iranians about the use of the (Syrian) airspace."

Many feel that neither Russia nor Iran, another staunch supporter of Damascus in the civil war, would like the idea of a Sunni area under Ankara's sway in Syria.

Both Bagci and Dilek do not believe that creating a Sunni area in northern Syria would serve Turkey's interests.

In Dilek's view, Turkey is not capable militarily or economically to establish or maintain such an entity in Syria, and it may come under U.S. sway and become part of the Kurdish-dominated area in the end.

"Turkey should calculate well the cost of such a move," Bagci said, adding that the Syrian military would easily take back Afrin from Ankara-backed rebels once the Turkish troops withdraw.