U.S. President Barack Obama insisted Friday that war weariness cannot excuse world powers from their duty to "respond to the gassing to death of hundreds of Syrian women and children."

U.S. President Barack Obama insisted Friday that war weariness cannot 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, he gave his clearest indication yet that the United States would indeed act.

His remarks came after the United States released an intelligence report claiming that the regime had launched a chemical attack in the suburbs of Damascus last week that killed 1,429 people, including at least 426 children.

"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."

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.

In a related context, 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 August 21 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.