Syrian President Bashar al-Assad said Russian airstrikes in Syria against Islamic State (ISIS) targets are more effective than those of the U.S.-led coalition because Moscow coordinates with his government.

He also disclosed that Syrian forces are gaining ground against the opposition in the ongoing civil war because the Russian airstrikes have tipped the balance in Syria's favour in some parts of the country.

The Syrian leader made the remarks during an interview with China's Phoenix Television Sunday, according to Fox News.

"You cannot fight with airstrikes alone," Assad told the TV station, adding that "Russian airstrikes are far effective because they cooperate with us."

He said Syrian troops had achieved victories in some areas even before the airstrikes began. However, he said his troops "could not be present everywhere in Syria."

"Following the participation of Russian air force in fighting terrorism, the situation improved well. I can say that the army now is advancing almost on every front," the Syrian leader said.

Syrian troops have captured dozens of villages in northern and western Syria since the Russian airstrikes began. Their biggest victory so far has been the lifting of a three-year ISIS siege on the military air base in Kweiras in the northern province of Aleppo, Fox News reported.

Russia, which began its bombing campaign against Syrian rebels and ISIS on Sept. 30, sharply raised the intensity of its airstrikes in recent days on President Vladimir Putin's order after ISIS confirmed that it brought down a Russian passenger jet over Egypt's Sinai Peninsula, killing all 224 people on board.

Asked if he is going to run for president again if early elections are held, Assad said: "It is my right, but it is early to say whether I will run or not."

"I will not say that I will not run if I see that this is needed," he added.

In a meeting in Viena last weekend, 17 nations have agreed with a peace plan for Syria that states that "free and fair elections would be held pursuant to the new constitution within 18 months."

This week, the U.S. State Department reportedly said that the clock starts once Assad's representatives and opposition figures begin talks on a constitution. The vote would determine a new parliament, though not necessarily a new president.