WASHINGTON (REUTERS) - The White House ruled out any military effort to oust Syrian President Bashar al-Assad from power on Tuesday, as President Barack Obama pondered options in response to last week's chemical weapons attack in Syria.

"The options that we are considering are not about regime change," said White House spokesman Jay Carney. "They are about responding to a clear violation of an international standard that prohibits the use of chemical weapons."

Mr Obama was considering cruise missile strikes against Syrian targets in response to the Aug 21 chemical weapons attack that US officials were increasingly confident was launched by the Syrian government.

Any attempt at "regime change" would draw the United States deeply into a conflict that Mr Obama had been determined to avoid. The President had already ruled out putting US troops on the ground in Syria.

The US wants Mr Assad to leave power, but as part of a negotiated political settlement with the Syrian rebels.

Mr Carney said the US had a variety of options from which to use, not just military options. Most of the talk about Syria in recent days, however, had been about a limited cruise missile attack.

Mr Carney reiterated that Mr Obama had not made a decision on how the US would respond to what it believed was an attack on civilians by the Syrian government.

"When the President has an announcement to make, he'll make it," he said.