BARACK Obama is facing increasing pressure to seek congressional support before taking action against Syria.
Dozens of politicians, most of them Republican, have signed a letter saying the president should not take military action without the approval of the US Congress.
And senior members of both political parties have urged the president to consult more closely before giving an order to launch hostilities.
Despite this, there has been little or no discussion about calling Congress back into session to debate the issue.
US politicians have been on a summer break for nearly a month, and are not due to return until 9 September.
Susan Rice faces her first key test as Mr Obama’s national security adviser in trying to convince a sceptical Congress that the US must respond to Syria’s apparent use of chemical weapons.
On Thursday evening, she moderated an unclassified telephone briefing by senior security aides to congressional leaders, as a first step in attempting to build consensus.
Meanwhile, US defence secretary Chuck Hagel said the Obama administration was consulting with allies to “further develop the facts” about last week’s alleged chemical weapons attack in Syria, and options for a response.
Speaking at a news conference in Manila, Mr Hagel said the administration also would continue to seek input from members of Congress on how the US should respond to the deadly attack.
He insisted the consultation on Thursday, involving Ms Rice, was “not to convince anyone of anything”.
It was intended as an update and a chance to solicit lawmakers’ views on possible US military action, Mr Hagel said.
“As we continue to consult with our allies, we’ll further develop the facts and intelligence on what happened,” he added.
Syria is facing the possibility of unilateral American military action within days.
Asked what the country’s president, Bashar al-Assad, could do to avoid a US strike, Mr Hagel said: “I have not been informed of any change in the Assad regime’s position on any issue.” As for the UK’s vote against British military action in Syria, Mr Hagel said London has strongly and publicly condemned Syria’s alleged gas attacks against civilians.
“That vote in the parliament doesn’t change that,” he said.
“Every nation has a responsibility to make their own decisions, and we respect that of any nation.
“We’ll continue to work with Britain and consult with Britain as we are with all our allies.
“As to international effort and collaboration, it is the goal of President Obama and our government that whatever decision is taken that it be an international collaboration and effort.”
He said the US would keep talking to the UK, and other nations, on “ways forward”.