MOSCOW—Russia chided its longtime ally Syria on Tuesday over its threat to use chemical weapons in case of a foreign attack, but Moscow gave no sign it was abandoning President Bashar Assad’s regime, despite growing international condemnation over the violence in the Arab country.

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In a statement that reflected a degree of irritation with Assad, the Russian Foreign Ministry reminded Syria that it had ratified a global convention banning the use of chemical weapons. It added that Russia expects Syria to “unfailingly honor its international obligations.”

The statement follows earlier Russian rebukes of Assad’s heavy-handed use of force and slow pace of reforms.