WASHINGTON, Aug 31: US President Barack Obama announced on Saturday that he would take military action against Syria but would do so only with congressional authorisation.

“After careful deliberation I have decided the United States should take military action against Syrian targets,” Mr Obama said. “I’m confident we can hold the Assad regime accountable for their use of chemical weapons.”

In a statement read at the White House Rose Garden, the president said that congressional leaders had agreed to schedule a debate and vote when they returned to session.

Standing with Vice President Joe Biden and a US flag fluttering behind him, Mr Obama declared: “We are prepared to strike whenever we choose. I’m prepared to give that order.”

He also said he had the authority under his executive powers to launch an attack, but believed that seeking a congressional vote was a better route.

The US Congress is scheduled to resume its session on Sept 9 after the summer recess and Mr Obama said his commanders had told him that a delay would not affect their capability to strike.

“The chairman of the Joint Chiefs has informed me that we are prepared to strike whenever we choose, moreover the chairman has indicated to me that our capacity to execute this mission is not time-sensitive,” he said.

“It will be effective tomorrow, or next week, or one month from now, and I am prepared to give that order.”

House Speaker John Boehner, a Republican, welcomed Mr Obama’s decision to seek congressional authorisation and said he expected the house to consider the measure in the week starting on Sept 9.

“Under the constitution, the responsibility to declare war lies with Congress,” the speaker said. “We are glad the president is seeking authorisation for any military action in Syria in response to serious, substantive questions being raised.”

As Mr Obama was leaving the garden after reading his statement, a reporter shouted if he would forgo the strike if Congress rejected his call but he did not respond.

It’s unclear if Congress would give him the authorisation he was seeking and Mr Obama also referred to this uncertainty in his statement, saying that after this week’s vote in Britain, some of his aides had also advised him not to go to Congress. The British parliament rejected a motion to participate in the US-led military operation in Syria.

But he decided to “seek authorisation for the use of force from the American people’s representatives in Congress,” Mr Obama said, adding that on Saturday morning he spoke to all four congressional leaders, and they agreed to schedule a debate and then a vote as soon as Congress came back into session.

“In the coming days, my administration stands ready to provide every member with the information they need to understand what happened in Syria and why it has such profound implications for America’s national security. And all of us should be accountable as we move forward, and that can only be accomplished with a vote,” he said.

“We cannot and will not turn a blind eye to what happened in Damascus … now is time to show the world that America keeps its commitments,” he said.

Mr Obama described the Aug 21 attack on a Damascus suburb as “an assault on human dignity,” which also “presents a serious danger to our national security”.

Hundreds of civilians were killed in the Aug 21 attack when Syrian forces allegedly fired chemical weapons at an opposition neighbourhood.

The Syrian government denies the charge, saying instead that the rebels have been using chemical weapons against their forces.

As Mr Obama spoke, hundreds of activists shouted anti-war slogans outside the White House, urging the president not to take their country into another war.

Some US lawmakers also have been urging Mr Obama not to launch military strikes in Syria but like the Speaker, they too welcomed his decision to consult Congress.

“The president’s role as commander-in-chief is always strengthened when he enjoys the expressed support of the Congress,” said Republican leader in the Senate, Mitch McConnell.

Senator Bob Corker, the top Republican on the Senate Foreign Relations Committee, said going to Congress was “absolutely the right decision”.

Another Republican leader, Senator John McCain, urged Mr Obama to do more than launching “cosmetic” strikes.

Mr Obama assured the American public, reluctant to get involved in yet another war after those in Afghanistan and Iraq, that he was not sending his troops to Syria.“This would not be an open-ended intervention. It would not put boots on the ground. Instead our action would be designed to be limited in duration and scope … deter this kind of behaviour and degrade their capacity to carry it out.”

President Obama’s announcement came hours after UN experts, who had been collecting samples from last week’s alleged chemical weapons strike, left the country for the Netherlands.