WASHINGTON -- Warning that President Bashar al-Assad of Syria has barely put a dent in his chemical weapons stockpile, President Obama's new envoy to the United Nations said on Friday that a failure to intervene in Syria would "give a green light to outrages that will threaten our security and haunt our conscience" for decades to come.
The envoy, Samantha Power, spoke at the Center for American Progress here. A longtime foreign policy adviser to Mr. Obama, she was in Washington partly to make the case for intervention, and to shore up Mr. Obama's skittish antiwar liberal base.
But outside the center's downtown building, members of the activist group Code Pink, who are opposed to the use of force in Syria, protested her appearance. Ms. Power left without taking questions.
"We have exhausted the alternatives," Ms. Power said. "For more than a year, we have pursued countless policy tools short of military force to try to dissuade Assad."
She added, "There is no risk-free door No. 2."
For Ms. Power, who assumed her new post at the United Nations in early August, the debate over Syria has been a searing test. At 43, she is a leading authority on genocide -- her 2002 book on the topic, "A Problem From Hell," won the Pulitzer Prize -- and perhaps the administration's most passionate human rights advocate.
But the inability of the United States to persuade the United Nations to act has left her stymied in a job she has held for barely a month. The Obama administration says it has evidence that the government of Mr. Assad used sarin gas in an Aug. 21 attack that killed 1,400 people, nearly a third of them children.
Through her new Twitter account, @AmbassadorPower, Ms. Power has kept up a steady stream of commentary denouncing the Assad regime. "Haunting images of entire families dead in their beds," she wrote on Aug. 26. "Verdict is clear: Assad has used CWs against civilians in violation of int'l norm."
On Thursday, after it became clear that Russia would block any move by the 15-member United Nations Security Council to take military action in Syria, Ms. Power said that the council had failed to fulfill its obligation to safeguard international peace and hold nations accountable for the use of weapons of mass destruction.
"Unfortunately, for the past 2½ years, the system devised in 1945 precisely to deal with threats of this nature did not work as it is supposed to," she said. "It did not protect peace and security for the hundreds of Syrian children who were gassed to death on Aug. 21."
This article originally appeared in The New York Times.