acknowledged on Friday that his attempt to seek congressional authorisation for punitive strikes against Syria was proving an uphill struggle and announced that he would take the case directly to the American people with a televised address.
Speaking after a G20 summit that failed to agree on a response to the use of chemical weapons in , the president repeatedly refused to be drawn on what he would do if Congress defied his arguments and voted against military authorisation.
"I'm not going to engage in parlour games about whether or not it's going to pass," Obama said.
The comments were contrasted sharply to the bullishness of the secretary of state, John Kerry, who said repeatedly in hearings on Capitol Hill this week that he expected Congress to vote yes. The administration was not contemplating any other outcome becuase the consequences were "too dire", Kerry said in one briefing.
In St Petersburg, Obama appealed in particular to members of the , where opposition to military action appears most strong, influenced by a series of opinion polls that show deep scepticism among the public. "Ultimately, you listen to your constituents, but you've also got to make some decisions about what you believe is right for America," Obama said. He confirmed that he would make a televised address on Tuesday.
Earlier on Friday, deputy national security adviser Tony Blinken told National Public Radio that Obama would not launch military strikes against Syria without congressional authorisation. "The president, of course, has the authority to act. But it's neither his desire, nor his intention, to use that authority absent Congress backing him," Blinken .
Obama refused to be drawn on what he would do in the event of Congress voting no, saying only he always knew that getting congressional authorisation was "going to be a heavy lift". Increasingly, Obama framed his argument as a historic national choice to be placed alongside checking the rise of Hitler or international failure to prevent genocide in Rwanda.
"When London was getting bombed, it was profoundly unpopular, both in Congress and around the country, to help the British. It doesn't mean it wasn't the right thing to do," said Obama.
"Imagine if Rwanda was going on right now. And we asked: should we intervene in Rwanda? I think it's fair to say that it probably wouldn't poll real well."
The president gave away few clues about his tactics on Capitol Hill, but amid rumours in St Petersburg that congressional votes until after a report from United Nations weapons inspectors, he hinted that this exercise might prove a more useful step than the administration previously hoped.
"I don't expect us to agree on this issue of chemical weapons use, although it is possible that after the UN inspector's report, it may be more difficult for Mr Putin to maintain his current positions about the evidence," Obama said.
A comprehensive UN report may help Washington in persuading the US electorate that an unacceptable line has been crossed in Syria that threatens to make everyone more vulnerable to chemical weapons in future.
Earlier the US pulled non-essential staff out of Turkey and and issued travel warnings to tourists as the threat of reprisals became a fresh fear weighing over its decision whether to attack Syria.
"Given the current tensions the region, as well as potential threats to US government facilities and personnel, we are taking these steps out of an abundance of caution to protect our employees and their families," the .
The that US intelligence had intercepted an order from Iran to militants in Iraq to attack the US embassy in Baghad if President Obama carries out his threat to respond aggressively to alleged Syrian chemical weapons use.
Threats to US interests in the Middle East are nothing new – last month it shut more than a dozen embassies in reaction to an alleged al-Qaida plot – but the rising tension over Syria brings fresh political difficulties for the administration as it tries to convince lawmakers that the risk of action of Syria is lower than the risk of inaction.
On Thursday night, senator John McCain, a leading advocate of broader US support for the Syrian rebels, was forced to repeatedly deny that American troops would be a risk from such engagement during a in his home state of Arizona.
McCain insisted he still has an open mind on US intervention, despite voting for on Wednesday.
and CNN both reported on Friday that Pentagon planners are now looking at the possibility of long-range bombers targeting Syria, possibly even from bases in the US, as well as just using cruise missiles stationed in the eastern Mediterranean. The Times also suggested that the Pentagon had been asked to extend range of targets under consideration, shifting the emphasis to the "degrade" part of what the White House has said is a mission to "deter and degrade" the chemical weapons capabilities of the Assad regime.
But polls show Obama's Syria proposals remain deeply unpopular and congressional leaders have yet to schedule a vote on military authorisation in the House of Representatives for fear that there is currently insufficient political backing on Capitol Hill.
There is also growing division internationally, despite attempts to build consensus during the summit in St Petersburg.
In Washington, the US ambassador to the United Nations, Samantha Power, used the most emotive language yet to put the US case for action against what she said was Syria's "uniquely monstrous crime".
She upped her attack on the UN security council, saying the institution was failing to do the job it was created for. "The international system that was founded in 1945 – a system we designed specifically to respond to the kinds of horrors we saw play out in world war two has not lived up to its promise or its responsibilities in the case of Syria,"
On Thursday, Power said the US had given up trying to work with the UN security council on Syria, accusing Russia of holding the council hostage.
In her speech to the Center for American Progress, Power also claimed there was a precedent for the president going against the wishes of Congress in launching humanitarian intervention, echoing minority leader Nancy Pelosi in recalling how the House of Representatives failed to pass a bill authorising President Clinton's action in Kosovo in 1999. "There is no risk-free door number two that we can choose in this case," added Power.