Russia, Syria, and Iran warned the United States on April 14 against launching new strikes on Syria and called for an international probe into a chemical attack there earlier this month.
Russian Foreign Minister Sergei Lavrov, who hosted his Iranian and Syrian counterparts at a trilateral meeting in Moscow, called last week's U.S. strike on a Syrian military base a "flagrant violation" of international law and warned that any further such action would entail "grave consequences not only for regional but global security."
Syrian Foreign Minister Walid al-Muallem said the meeting sent a "strong message" to Washington. Iran's Mohammad Javad Zarif emphasized that the participants warned that any unilateral action by the U.S. is unacceptable.
Washington has blamed the Syrian government for launching a deadly chemical attack in Khan Sheikhun that killed more than 80 people on April 4, and responded by striking a Syrian air base.
Moscow and Damascus have said the victims were killed by toxic agents released from a rebel chemical arsenal and warned against putting the blame on Syria until an independent inquiry has been conducted.
Russia has been Syrian President Bashar al-Assad's most important backer and has been involved in military operations on the side of Assad's government since September 2015.