U.S. says it saw preparations for possible Syria chemical attack

Syria's President Bashar al-Assad visits a Russian air base at Hmeymim, in western Syria in this handout picture posted on SANA on June 27, 2017, Syria. SANA/Handout via REUTERS

WASHINGTON/MOSCOW (Reuters) - A U.S. warning to Syria's leadership against staging a chemical weapons attack was based on intelligence about what appeared to be active preparations at a Syrian airfield used for such an attack in April, U.S. officials said on Tuesday.

Russia, Syrian President Bashar al-Assad's main international backer, denounced the warning and dismissed White House assertions that a strike was being prepared as "unacceptable," raising the tension between Washington and Moscow over the Syrian civil war.