By Tabassum Zakaria
WASHINGTON (Reuters) - Samantha Power, in her first major speech as U.S. ambassador to the United Nations, argued Friday that a limited military strike was the only option left to respond to a chemical weapons attack in Syria after diplomatic efforts had stalled.
"Some have asked, given our collective war-weariness, why we cannot use non-military tools to achieve the same end? My answer to this question is: we have exhausted the alternatives," Power said at the Center for American Progress.
Power spoke as President Barack Obama struggled to convince Congress to approve a military strike against Syria for its alleged use of chemical weapons against its own people on August 21.
Syrian President Bashar al-Assad, she said, "has barely put a dent in his enormous stockpile. And the international community has clearly not yet put a dent in his willingness to use them."
Power, a lawyer and human rights advocate who wrote the book "A Problem from Hell" about inaction on genocides, described the chemical weapons attack as an "atrocity" and "murderous behavior." U.S. intelligence agencies have said 1,429 people were killed, including at least 426 children.
She lay blame for diplomatic obstacles on Russia just hours after Obama, attending an international summit, held a news conference in St. Petersburg in which he avoided saying whether he would take military action in Syria if the U.S. Congress voted against it.
"Russia, often backed by China, has blocked every relevant action in the Security Council," Power said.
"In Assad's cost-benefit calculus, he must have weighed the military benefits of using this hideous weapon against the recognition that he could get away with it because Russia would have Syria's back in the Security Council," she said.
About a dozen anti-war protesters gathered outside the building's entrance where Power was speaking.
"If we cannot summon the courage to act when the evidence is clear, and when the action being contemplated is limited, then our ability to lead in the world is compromised," she said.
(Editing by Fred Barbash and Eric Walsh)