"The White House published a statement full of lies about the use of chemical weapons in Syria, based on fabricated information, through which it is trying to hold the Syrian government responsible for such use," state news agency SANA quoted a foreign ministry official as saying.

The official said the US claims came "after reports affirming that armed terrorist groups active in Syria are in possession of deadly chemical weapons and the technology necessary to make them".

Washington claimed on Thursday there was evidence that the Syrian government had used chemical weapons including sarin nerve gas in attacks that killed up to 150 people.

The US administration also confirmed it would now provide "military support" to terrorist group in Syria, a decision condemned by Damascus.

"The American decision to arm armed terrorist groups demonstrates... the direct involvement of the United States in the Syrian bloodbath," the official said.

"This raises serious questions about their good faith when it comes to finding a political solution in Syria," the official added.

Washington and Moscow have been spearheading efforts to organize a conference in Geneva to find a political solution to the Syrian conflict.