Russia should reconsider its continued support to Syrian President Bashar Assad’s regime, U.S. Secretary of State Rex Tillerson said on ABC’s “This Week” interview with George Stephanopoulos that aired Sunday. The comments came after the U.S. carried out missile strikes on March 6 on the Syrian government-controlled Shayrat air base in retaliation to a fatal chemical gas attack earlier that week in Idlib province that killed nearly 100 people.

Tillerson suggested in the interview that Russia is partially responsible for the Syrian government’s actions such as the latest chemical attack. But he said he is hopeful that Washington and Moscow will have “constructive talks” resulting in a solution to the conflict in the war-torn country.

“Clearly, they [Russia] are Bashar Assad's current ally. They should have the greatest influence on Bashar Assad, and certainly his decisions to use chemical weapons, they should have the greatest influence on him to cause him to no longer use those,” Tillerson told Stephanopoulos during the interview.

“I hope that Russia is thinking carefully about its continued alliance with Bashar Assad, because every time one of these horrific attacks occurs, it draws Russia closer in to some level of responsibility,” the secretary of state added.

While authorities in the U.S. are probing Russia’s role in the chemical gas attack, Lt. Gen. H.R. McMaster — also the current national security adviser — said Moscow should be pushed to answer whether it knew about the attack beforehand.

“I think what we should do is ask Russia — how could it be, if you have advisors at that airfield, that you didn't know that the Syrian air force was preparing and executing a mass murder attack with chemical weapons? I think we ought to ask them a question,” McMaster said on “Fox News Sunday.”

Separately, British daily the Sunday Times reported that U.K. Foreign Secretary Boris Johnson wants the G7 to release a joint declaration saying that Russia should withdraw its support to Assad and pull out its forces from Syria. If Russia does not end its support to Assad, Britain will push Western countries to impose new sanctions on Russia, the paper reported.

Following this, the Russian Embassy in London took to Twitter asking its followers the probable outcomes if the expected G7 ultimatum to Russia led to a war. The options included: “war of clowns, war of muses, a conventional war or a mix of the above.”

The embassy posted another tweet asking, in case of a war scenario, what trust people have on U.S. President Donald Trump as a “wartime leader” and Johnson as his “lieutenant.”

Trump and Johnson did not respond to the tweets.