NEW YORK, July 15. /TASS/. The US is considering a number of military options to address the allegedly increasing Russian activity in the skies over Syria, Associated Press reported on Friday citing a defense official.

The actions by the Russian aviation "complicated efforts to strike" a leader of the Islamic State group (a terrorist organization banned in Russia - TASS) last weekend, the official said without detailing the options. The Russian military activity, which has increased in frequency and aggression since March, stems from growing cooperation and coordination between Moscow, Tehran and the Syrian government to try to pressure the US to leave Syria, according to the official.

There are concerns that Russian pilots will knock a Reaper drone out of the sky and that Moscow believes that type of action would not get a strong US military response, the defense official said. However, "the US does not believe Russian aircraft plan to drop bombs on US troops or shoot down manned aircraft," the agency said citing the official. The US will not cede any territory and will continue to fly in the western part of the country on anti-Islamic State missions, the official noted.