Any US military action against Syria would amount to “support for al-Qaeda and its affiliates,” Damascus has said.

Syrian Deputy Foreign Minister Faisal Mekdad also told the BBC that armed groups backed by America – not Syrian troops – had used chemical weapons.

The US says it has evidence that Damascus used the nerve agent sarin in a deadly attack in August.

President Barack Obama has vowed punitive action but wants Congress to vote on the issue first.

The alleged chemical attack took place on 21 August in the eastern suburbs of Damascus. The US says more than 1,400 people were killed, including 426 children.

The French government has said it will hand over its own evidence to French lawmakers on Monday, linking the Syrian regime to the attack.

“It will be a set of evidence of different kinds that will allow the regime to be clearly identified as responsible for the August 21 chemical attack,” a government source told the French news agency AFP.

There is growing pressure for French President Francois Hollande to hold a parliamentary vote on the issue, in line with Britain and the US.

The French parliament is due to debate the issue on Wednesday.

US lawmakers are due to reconvene next week, and White House officials have said they believe they will support the president.

Campaigning to convince people and politicians that military intervention is the right way forward has already begun in America, correspondents say.

But by putting off an attack and seeking congressional approval, President Obama has taken the biggest gamble of his presidency, the BBC’s North America editor Mark Mardell says.

He adds that if Congress does not back him, it would be disastrous for the president and his decision to call for a vote would look foolish.

In other developments:

• UN experts have gathered evidence in Syria to determine whether chemical weapons attacks have taken place – and they are now analysing samples
• Arab League foreign ministers urged the world community to “take the deterrent and necessary measures” against Syria. But several members – including Lebanon and Iraq – did not back the call
• Jordan – a key US ally in the region – ruled out joining any US-led coalition against Damascus

‘Hatred for Americans’

Mr Mekdad told the BBC’s Jeremy Bowen in Damascus: “Any attack against Syria is support for al-Qaeda and its affiliates, whether Jabat al-Nusra or the State of Islam in Syria and Iraq.”

Jabat al-Nusra and other groups linked to al-Qaeda have come to play a significant role in the fight against President Assad’s government.

Mr Mekdad – who is considered to be highly influential within President Bashar al-Assad’s government – also warned that possible US intervention would deepen “hatred for the Americans” and destabilise the whole Middle East.

He said that Mr Obama’s surprise decision to seek congressional approval for strikes showed that he had not thought through all the “consequences”.

But he added: “This did not change anything, since he (President Obama) is determined to launch an attack”.

As for a vote in Congress, Mr Mekdad said it would base its decision on whether attacking Syria was in the interests of Israel.

‘Case is building’

US Secretary of State John Kerry said on Sunday that Washington had evidence that sarin was used in the 21 August attacks.

He said samples from hair and blood gathered afterwards had “tested positive for signatures of sarin”.

Mr Kerry implied that the US evidence was supplied by its own sources, rather than via the UN inspectors.

“In the last 24 hours, we have learned through samples that were provided to the United States that have now been tested from first responders in east Damascus and hair samples and blood samples have tested positive for signatures of Sarin,” Mr Kerry said on NBC’s Meet The Press.

The US has previously said it had similar evidence of sarin use in other attacks.

Mr Kerry also said he was confident Congress would give its approval for the US to launch strikes against Syria.

Congressmen “will do what is right because they understand the stakes”, he said, declining to explain whether Mr Obama would press ahead even if Congress voted against.

However, some lawmakers have expressed doubts about Mr Obama’s plan for a “limited, narrow” operation.

“I’m still very sceptical. It is not clear to me that we know what the results of this attack will be, meaning, will it be effective?” said Jim Himes, a Democratic member of the House of Representatives.

“It’s not clear to me what response might be undertaken by Iran, by the Syrians, against Israel, against us, in the realm of terrorism. It is also not at all clear that we’ve got any really, international, support,” he added.

Syria is known to have extensive supplies of chemical weapons.

Mr Obama has often said that using them would cross a “red line”, prompting US intervention.

Damascus has been fighting rebel forces since March 2011.

More than 100,000 people are estimated to have died in the conflict, and at least 1.7 million have become refugees.

• Five US destroyers – USS Gravely, USS Ramage, USS Barry, USS Mahan and USS Stout – are in the eastern Mediterranean, equipped with cruise missiles. The missiles can also be fired from submarines, but the US Navy does not reveal their locations

• Airbases at Incirlik and Izmir in Turkey, and in Jordan, could be used to carry out strikes

• Two aircraft carriers – USS Nimitz and USS Harry S Truman are in the wider region

• French aircraft carrier Charles de Gaulle is currently in Toulon in the western Mediterranean

• French Rafale and Mirage aircraft can also operate from Al-Dhahra airbase in the UAE