"We should exclude the danger of terrorists purchasing materials that can be used as a weapon of mass destruction," Mr. Trubnikov pointed out.
"Both we and the Americans proceed from the assumption that it is necessary, first, to enhance protection of such facilities, and, second, to constantly monitor what means terrorists could have today, tomorrow and the day after tomorrow," he said.
He also emphasized that biological weapons are the simplest ones for terrorists today.
Dirty nuclear weapons represent a great threat for people if used, for instance, to contaminate the water supply, the diplomat said.
"We did not say that somebody will drop a nuclear bomb," Mr. Trubnikov said and added that terrorists can use less sophisticated but no less dangerous forms of WMDs.
"The threat of using a dirty bomb is real," he concluded.
Mr. Trubnikov is a co-chairman of the Russian-American working group for combating terrorism, which completed its 11th session on Thursday in Washington.
The next session will be held in October in Moscow.