Washington -President Barack Obama insisted on Friday that war weariness could not excuse world powers from their duty to respond to the gassing to death of hundreds of Syrian women and children.
While noting that he had made no "final decision" on striking Syria to punish Bashar al-Assad's regime, he gave his clearest indication yet that the United States would indeed act.
His remarks came after the United States released an intelligence report expressing "high confidence" that the regime had launched a chemical onslaught in the suburbs of Damascus that killed 1 429 people, including at least 426 children, last week.
"This kind of attack is a challenge to the world," Obama said in brief remarks to reporters at the White House.
"We cannot accept a world where women and children and innocent civilians are gassed on a terrible scale," he said, calling the attack a threat to US "national security interests.
"I have said before, and I meant what I said, that the world has an obligation to make sure we maintain the norm against the use of chemical weapons," he said, slamming the "incapacity" of the UN Security Council to act.
Obama said his administration and the military were looking at a "wide range of options" but had ruled out "boots on the ground" or a "long-term campaign.
"We are looking at the possibility of a limited, narrow act," he said.
France gave its backing to the US plans, but British lawmakers voted against any involvement in military action and other close allies including Germany said they would not sign up.
Russia, Syria's most powerful ally, has meanwhile questioned US intelligence on the 21 August gas attacks and has warned against any military strikes without UN backing.
In Damascus, UN experts completed their investigation into the attacks east of the capital and said they would "expedite" a report on whether chemical weapons had been used there.
The team is due to leave the war-battered country on Saturday and report back immediately to UN chief Ban Ki-moon, who has appealed to the West to allow time for their findings to be assessed.
US Secretary of State John Kerry cited "multiple streams of intelligence" indicating that the Syrian government had carried out the attack and that Assad himself is the "ultimate decision maker" for the country's chemical weapons program.
Kerry said failure to act would not only erode the nearly century-old norm against the use of chemical weapons, but would embolden Syrian allies Iran and Hezbollah.
Gruesome pictures of some of the reported victims of the attacks, including children, have shocked the world and piled on the pressure for a response that could draw a reluctant West into the vicious Syrian civil war.
But Russia and Iran, and even some US allies have warned against any intervention, saying it risked sparking a wider conflict.
Divisions over Syria have further chilled the frosty relations between Washington and Moscow ahead of the G20 summit in Saint Petersburg next week, where pointedly there will be no face-to-face talks between Obama and Russian President Vladimir Putin.