The US decision to militarily attack Syria "is a fragrant imperialist act of aggression", the Communist Party of India-Marxist (CPI-M) said on Monday.
"This latest intent of US aggression against a sovereign country is on the pretext that the Syrian government used a chemical weapon against the rebel forces," the CPI-M said in a statement.
"This charge has neither been substantiated nor is it clear who used the nerve gas. This is reminiscent of the charge of 'weapons of mass destruction' used to invade Iraq in 2003."
The CPI-M said the US and its allies had been arming and financing the rebels to topple the Syrian government.
"The decision to militarily attack Syria is a flagrant imperialist act of aggression."