The Taliban, ousted from power after a U.S.-led military operation in 2001, have been stepping up their activities in recent months. The radical Islamic movement has vowed to increase attacks in order to undermine the authority of the current Afghan administration.
"Despite the annual increase in the numbers of foreign troops in Afghanistan, the Taliban's area of influence in the country is constantly growing," Zamir Kabulov told reporters after a Russia-NATO Council meeting in Brussels.
"I believe that the Taliban have an influence in more than half of Afghanistan's territory and control up to 20% of that area," he said, adding that there are many places that "are off limits to foreign troops".
The ambassador said that despite the six-year-long international peacekeeping operation in Afghanistan, in which NATO plays a key role, "The situation in Afghanistan in general continues to deteriorate."
Responding to a question from a RIA Novosti reporter, he said that the NATO-led coalition force had 53,000 personnel, plus, "on paper," 62,000 in the National Afghan Army and 70,000 in the Afghan police.
He said that this force was fighting against some 2,500 "professionally trained militants."
Kabulov said it was critical for NATO to change its tactics and strategy in Afghanistan.
"Any further increase in NATO's military presence (in Afghanistan) will not solve the problem," he said, adding that the only way out for NATO was "the creation of a battle-worthy Afghan army and police force."