A meeting of the "likeminded" countries was hastily arranged on the sidelines of a Group of 7 industrialized economies in Italy, days after the US for the first time launched airstrikes against Syrian President Bashar Assad's forces.
Diplomats gathered in Italy as US officials in Washington floated the possibility of new sanctions on the Syrian and Russian military.
At Tuesday's meeting in the walled Tuscan city of Lucca, the G-7 countries were joined by diplomats from Muslim-majority nations including Jordan, Qatar, Saudi Arabia, Turkey and the United Arab Emirates, the Associated Press reported.
Seated around long tables in an ornate, red-walled room, the diplomats smiled and exchanged pleasantries but made no remarks as photographers were allowed in briefly for the start of the meeting. The session lasted roughly an hour.
That accusation will hang over Tillerson's visit to Moscow, where he plans with meet with Russia's foreign minister and possibly with Russian President Vladimir Putin. The Kremlin declined to say whether Putin would meet with Tillerson, in line with its usual practice of not announcing such meetings ahead of time.
The US military attacked the Syrian government’s Shayrat Airfield near Homs with 59 tomahawk missiles on Friday.
Officially announcing the strike, US President Donald Trump claimed that the targeted airfield had launched the chemical attack on the rebel-held area in Idlib.
Earlier on Thursday, Syrian Foreign Minister Walid Muallem said the country’s armed forces "did not and will not" use chemical weapons, even against extremist groups.