In this file photo provided on Tuesday, March 15, 2016, by the Russian Defense Ministry Press Service, a lineup of Russian troops is held at Hemeimeem air base in Syria (Vadim Grishankin/Russian Defense Ministry Press Service via AP, file)

Russia grew to be "more aggressive" in terms of its behavior in Syria since the beginning of the war in Ukraine, US Air Forces Central Command's head, Lieutenant General Alexus Grynkewich said Monday.

"The Russian presence in Syria has become, I would argue, more aggressive since the Ukrainian invasion," Grynkewich said during a conference that brought together the Air and Space Forces.

One might be able to explain the new Russian stance in Syria by studying Moscow's "military failures in Ukraine coupled with Russian generals seeking to regain a better standing within the Russian armed forces," Grynkewich told the Air and Space Forces Association conference.

The US forces in Syria note an increased pressure in air and on the ground from Russian forces and the Pentagon finds it "a bit concerning," the military official revealed.

The Israeli occupation said in late July that its fighter jets were attacked by Russian anti-aircraft systems during a flight over Syria in May in what "Tel Aviv" said was a "one-off incident".

The Israeli occupation made the revelation amid tensions with Russia over "Tel Aviv's" support for Kiev in the midst of the Ukraine war and Moscow's dissolution of the Jewish Agency for "Israel" on its territories.

Russian Deputy Foreign Minister Mikhail Bogdanov said earlier in the day that Moscow was ready to discuss the situation in Syria with the United States.

More than 45 Jabhat Al-Nusra militants have been killed in a Russian airstrike in Syria's Idlib province, Major General Oleg Egorov, deputy head of the Russian Defense Ministry's Center for Reconciliation of Opposing Sides in Syria, confirmed on Sunday.

According to Egorov, the terrorists killed in the strike were directly involved in attacks on Syrian soldiers and civilians, as well as preparing for sabotage and terrorist activities in Idlib.

Earlier, Egorov warned that US-supported militants are in the works of carrying out a false-flag attack against civilians in the strategic Al-Tanf region, located near the borders of Iraq and Jordan, to incriminate Syrian government forces.

The report added that the US military are intending to intensify the presence of Maghawir Al-Thawra terrorists and allied Takfiris, with the aim of deploying them to areas in the Northern and Eastern parts of Syria under the control of the militants from the US-supported so-called Syrian Democratic Forces (SDF).