Moscow said Wednesday that it was useless to give Russia an ultimatum, in response to the United States' top diplomat urging it to stop supporting the Syrian government regime.

US Secretary of State Rex Tillerson, who arrived in Moscow on Tuesday after a G7 meeting in Rome, was on Wednesday set to meet his Russian counterpart Sergey Lavrov for talks expected to focus on the situation in Syria.

"It seems to me that everyone has already understood that it is useless to travel to us with ultimatums, it is simply counterproductive," said Foreign Ministry spokesperson Maria Zakharova.

It was uncertain whether Tillerson would be meeting with Russian President Vladimir Putin as it was not part of the agenda but the Kremlin had not ruled out the possibility.

Tillerson's Moscow visit made him the first senior American official to visit Russia since US President Donald Trump came to power.

In a statement published on the Department of State's website, Tillerson suggested Russia choose between supporting the regime of Syrian President Bashar al-Assad and an alliance with the West.

"Is that a long-term alliance that serves Russia's interest, or would Russia prefer to realign with the United States, with other Western countries and Middle East countries who are seeking to resolve the Syrian crisis?" Tillerson said ahead of his trip to Moscow.

Since a suspected chemical attack on Apr. 4 in the northern Syrian province of Idlib, the US has accused Russia of being morally responsible for the deaths of almost 100 Syrian civilians.

The US last week launched air strikes on a regime airbase in response to the alleged chemical attack.