The attack lacked a United Nations Security Council mandate, and the US Congress was not even consulted.
Russia and the US have been supporting opposite sides during the now-six-year militancy in Syria. Moscow has been helping Damascus in its fight against extremist militants, while Washington has been arming some of the militant groups fighting in Syria. The US has also been leading dozens of its allies in a coalition purportedly targeting Daesh positions in the Arab country.
Observers said the US missile attack against the Syrian airfield threatened to spark a major confrontation between powers Russia and the US.
Russian President Vladimir Putin said afterwards that the strike had seriously hurt the Russo-American ties. Moscow also shut down a hot line that had been set up to prevent clashes between the Russian and American militaries in Syria.
Washington staged the strike over the accusation that Damascus had used the base to launch a gas attack in the northeastern Syrian province of Idlib a few days earlier. Syria has denied the accusation, saying instead that a chemical weapons depot belonging to the anti-Damascus militants had been hit in a conventional Syrian airstrike. Russia has verified that account.
Lavrov also told Tillerson that Russia had questions about the "very ambiguous” and "contradictory” statements coming from the US regarding Syria. He added that the Kremlin wanted to know about the real intentions of the White House as far as Syria was concerned.
He was apparently referring to Washington’s recent policy reversals and contradictory statements from US officials on Syria.
On Wednesday, Trump, an early advocate of closer cooperation with Russia on Syria and a personal admirer of Putin, told Fox Business Network that the Russian president’s support for Assad was "very bad for Russia.”
Lavrov also said that he expected "frank and honest” discussions with Tillerson on forming a broad anti-terrorism coalition during the US secretary of state’s stay in Moscow.