US President Barack Obama waves as he returns to the White House in Washington August 23, 2013. [Photo/Agencies]

WASHINGTON - President Barack Obama spoke with Australian Prime Minister Kevin Rudd on Monday about possible international responses to the Syrian crisis while his national security adviser discussed Syria and security with Israeli officials, the White House said.

In a call with Rudd, "the two leaders expressed their grave concern about the reported use of chemical weapons by the Syrian regime against civilians near Damascus on Wednesday," the White House said in a statement. They "discussed possible responses by the international community," it said.

National security adviser Susan Rice hosted a delegation led by Yaakov Amidror, the chairman of Israel's National Security Council. The meetings were part of a series of regular high-level bilateral consultations and touched on Iran, Egypt, Syria, and other regional security issues, the White House said.

In their strongest condemnation of Syria to date, Obama administration officials said on Monday it was undeniable chemical weapons had been used and that there was little doubt the Syrian government was responsible for an attack that claimed the lives of hundreds of men, women and children.

"The president and his team are evaluating options with regards to responses to this specific violation of an international norm - the prohibited use of chemical weapons against civilian populations," White House spokesman Jay Carney told reporters.

Carney said a military response is among the options under consideration.

As Obama mulls the possibilities, US officials have made clear they want to win international support before taking any actions, and the administration has begun a series of consultations with allies. The president spoke over the weekend with British Prime Minister David Cameron and French President Francois Hollande.

Australia's Rudd, a former diplomat whose country is a close US ally and takes the rotating UN Security Council chair from Sunday, said the international principles behind the events in Syria were clear.

"I do not believe the world can simply turn a blind eye to the use of chemical weapons against a civilian population resulting in nearly 300 deaths, or more, and some 3,600 people hospitalized," he said in a speech in Sydney on Tuesday.

Taking no action, he said, would send a message of impunity to "every autocracy in the world contemplating the future use of chemical weapons".