The head of Syria's parliament has urged the US Congress to vote against military action targeting the Syrian regime, state news agency SANA said.

"We urge you not to take reckless measures as you have the power to steer the United States from the path of war to that of diplomacy," SANA quoted parliament chief Jihad al-Lahham as saying on Friday.

The message is intended to be sent to every member of the US Congress before they vote on a request from US President Barack Obama for authorisation to use military force against Syria.

Obama has proposed limited strikes in response to an alleged chemical weapons attack on August 21, which Washington says was carried out by the Syrian government, a charge it denies.

"Any military intervention would be illegal because Syria is a sovereign country and does not represent a threat to the United States, and any strike would not be authorised by the [UN] Security Council," Lahham said.

Earlier this month, Foreign Minister Faisal Meqdad urged the US Congress to "show wisdom" on the issue of authorising military strikes against Syria.

President Bashar al-Assad has also warned of the consequences of any such action.

"We cannot only talk about a Syrian response, but what could happen after the first strike," Assad said in an interview with Le Figaro newspaper.

"Everyone will lose control of the situation once the powder keg explodes. Chaos and extremism will spread. There is a risk of regional war."

Russian warnings

Meanwhile, Russia warned the United States against targeting Syria's chemical arsenal as Washington considered the use of force against Assad's regime.

"With particular concern we perceive the fact that military infrastructure facilities securing the integrity and safety of Syria's chemical arsenal are among the possible targets for military strikes," the Russian Foreign Ministry said in a statement on Friday.

"In this respect we warn US authorities and their allies against striking any chemical facilities and adjacent territories," the statement said.

"Such actions would represent a dangerous new turn in the tragic development of the Syria crisis," the ministry said, warning that the strikes could prompt the release of highly toxic substances.

"Besides, one cannot rule out that militants and terrorists would gain access to chemical weapons or chemical warfare agents as a result of such a reckless move," the ministry said, expressing concern over the possible spread of chemical weapons further across Syria and beyond its borders.

"The US bombing of Iraq's Al Muthanna chemical storage facility led to a serious contamination of adjacent territory in 1991," the statement said.

"For peaceful residents of Syria and other countries of the region the consequences can be even more severe."

The warnings from the Russian foreign ministry came as both President Vladimir Putin and US President Barack Obama reiterated their positions against and for military action in Syria during speeches made at the G20 summit in St Petersburg.