U.S. soldiers guard at the site of a suicide bombing in Kabul, Afghanistan, Feb. 26, 2015. (Xinhua/Ahmad Massoud)

MOSCOW, Aug. 14 (Xinhua) -- The U.S. military campaign in Afghanistan has failed and Washington should withdraw its troops from the country, Special Representative of the Russian President for Afghanistan Zamir Kabulov said Monday.

"Since the U.S. Army is unable to do anything serious, let it leave Afghanistan," Kabulov was quoted by the Russian newspaper Izvestia as saying.

He said that, in spite of the U.S. presence in Afghanistan, the country is becoming a "global incubator of international terrorism."

Kabulov said Moscow also opposes the idea of replacing the regular U.S. soldiers in Afghanistan with mercenaries, which has been increasingly discussed in the military circle in Washington.

Former U.S. President Barack Obama planned to reduce the number of U.S. troops in Afghanistan from 9,800 to some 5,500 by the end of 2015 and withdraw all troops by the end of 2016 when his presidency came to an end.

However, given the deteriorating security situation in Afghanistan, the Obama administration repeatedly postponed the withdrawal.

Currently, there are about 8,400 U.S. troops and 5,000 forces from other members of the North Atlantic Treaty Organization on the ground in Afghanistan to train and assist the Afghan forces against the Taliban and conduct counter-terrorism missions.