MOSCOW, June 20. /TASS/. Russian Foreign Minister Sergey Lavrov has pledged to ask U.S. Secretary of State Rex Tillerson why Washington is delivering no strikes on Jabhat al-Nusra (a terrorist organization outlawed in Russia - TASS).

"There is a mechanism which has now been suspended after the United States downed [Syrian] planes. Our defense ministry has requested detailed explanations and we expect to have them," Lavrov said. "This mechanism functioned quite well. The Americans represented not only themselves but the entire coalition."

In his words, Turkey, as a member of the "Astana process," had influence on certain armed groups on the ground. "Iran, as a member of this process, also influences other groups. If we view the situation from this angle, especially as soon as the Astana process has gained a sustainable character, we can see that there are grounds to focus on anti-terrorism efforts," the Russian top diplomat noted.

"I don’t want to make guesses that someone might not be happy over that and that incidents with strikes on government forces give away plans to wreck the effectiveness of the anti-terrorist efforts. But we cannot but recall that over the entire period of the crisis there has been an impression that Jabhat al-Nusra has been exempt from strike," he said.

"I will ask this question to Rex Tillerson in the immediate future," Lavrov pldedged. "There must be absolute clarity about that. Facts demonstrate that the coalition is indeed hitting Islamic State positions but we cannot say that fight against al-Nusra is vigorous as well.".