Moscow: Russian Foreign Minister Sergey Lavrov said Saturday that the United States had apologized to Syrian President Bashar Assad for the airstrikes against Syrian government troops.

"Yes, they have apologized," Xinhua news agency quoted Lavrov as saying in an interview.

Commenting on restoring truce in the war-battered country, Lavrov said it is only possible on a collective basis, which need the "sincere" cooperation from Washington to separate the so called moderate opposition from terrorist groups.

On September 17, the US-led coalition airstrikes killed over 60 Syrian government troops and injured some 100 others in Syria`s eastern province of Deir al-Zour, incurring a strong response from Moscow, which accused Washington of violating the cease-fire accord in Syria.

On September 10, Lavrov and US Secretary of State John Kerry announced a nationwide cease-fire in Syria, which demands all warring sides stop attacks and airstrikes, and allow access to besieged areas, including Aleppo.

However, crossfire has resumed in the first hours after the truce deal expired on Monday.