UN Secretary General Antonio Guterres (R) meets with Syria's Foreign Minister Walid Moualem on September 21, 2017 at the United Nations in New York. (AFP Photo)

DAMASCUS, Sept. 23 (Xinhua) -- Syria's foreign minister said Saturday that complete victory was within reach in the country and Damascus hopes de-escalation zones will help Syria reach a cessation of hostilities, state news agency SANA reported.

"The liberation of Aleppo and Palmyra, the lifting of the siege of Deir al-Zour and the eradication of terrorism from many parts of Syria prove that victory is now within reach," Foreign Minister Walid Muallem said in his speech at the United Nations General Assembly.

U.S.-backed Syrian fighters captured Saturday the country's largest gas field from the Islamic State group in an eastern province that borders Iraq as they race with government forces to capture the energy-rich region, a senior official with the group said.

Nasser Haj Mansour of the Syrian Democratic Forces said the Conoco gas field and plant came under full control of the group on Saturday morning after days of fighting with the extremists.

Deir al-Zour is a province rich in oil and gas and both sides have been racing to reach the fields.

The next main target will be al-Omar oil field which is Syria's largest oil field and is also on the east bank of the Euphrates. Syrian government forces are also speeding to capture it.

Russia has warned against targeting its special forces in Deir al-Zour, raising concerns over direct clashes between rival forces backed by Moscow and Washington fighting for the energy-wealthy region.

Russia has been a main backer of Syrian President Bashar al-Assad and joined the war two years ago tipping the balance of power in his favor.