Updated at 6:08 p.m. ET
A military strike in Syria may be unpopular, but it's the right thing to do for the security of America and the world, President Obama argued Friday.
"There are times where we have to make hard choices if we're going to stand up for the things we care about," he explained at a press conference in St. Petersburg, Russia during the G-20 global economic summit. "I was under no illusions when I embarked on this path, but I think it's the right thing to do."
He noted that much of the American public and the international community remains opposed to his call for military action in Syria, spurred by evidence that the Syrian regime under President Bashar Assad killed almost 1,500 civilians in an August 21 chemical weapons attack. But that shouldn't stop us from doing what we need to do, he argued, warning that failure to respond to the chemical attack would undermine the international norm prohibiting the use of weapons of mass destruction.
"This is not convenient. This is not something that I think a lot of folks around the world find an appetizing set of choices," he admitted. "But the question is 'Do these norms mean something?' And if we're not acting, what does that say?"
"I was elected to end wars, not start them," he said. "I spent the last four and a half years doing everything I can to reduce our reliance on military power as a means of meeting our international obligations and protecting the American people."
"I would greatly prefer working through multilateral channels and working through the United Nations to get this done," he said, but "when there's a breach this brazen, of a norm this important, and the international community is paralyzed and frozen and doesn't act, then that norm begins to unravel."
After the president spoke, in an attempt to demonstrate international cohesion, the White House released a joint statement from the U.S. and 10 other countries that condemned "in the strongest terms" the chemical attack.
"The evidence clearly points to the Syrian government being responsible for the attack, which is part of a pattern of chemical weapons use by the regime," the statement read. "We call for a strong international response to this grave violation of the world's rules and conscience that will send a clear message that this kind of atrocity can never be repeated. Those who perpetrated these crimes must be held accountable."
As the debate continues, "I will make the best case that I can to the American people as well as to the international community," Mr. Obama said, pledging to address the nation from the White House on Tuesday to make his case.
"It's conceivable that at the end of the day I don't persuade a majority of the American people that it's the right thing to do," he conceded. "And then each member of Congress is going to have to decide...You listen to your constituents but you've also got to make decisions about what you believe is right for America."
"I trust my constituents want me to offer my best judgment," he said. "That's why they elected me. That's why they reelected me."
Back in the U.S., Senate Majority Leader Harry Reid formally filed the resolution authorizing the use of force on Friday, queuing up a likely vote next week on the resolution's final passage. A vote in the House is expected to follow.
In St. Petersburg, the president rebutted a report claiming his administration hasas "inaccurate," and he signaled he is open to alternative proposals that could delay or replace military action.
Asked specifically about a plan from Sens. Joe Manchin, D-W.V., and Heidi Heitkamp, D-N.D. that would give Syria 45 days to sign an international chemical weapons ban before deciding on any military action, the president was noncommittal but he didn't close the door.
"I am listening to all these ideas and some of them are constructive," he said.
The president also addressed his conversation with Russian President Vladimir Putin, who is skeptical that Assad's regime was responsible for the chemical attack and has stymied multilateral action against Syria with Russia's veto power in the United Nations.
During his own press conference earlier Friday, Putin described his talk with the Mr. Obama as a "constructive and friendly conversation - or at least it was held in a friendly atmosphere."
"We all retained our own opinions, but there is a dialogue," he said. "I don't agree with his arguments, and he doesn't agree with mine. But we hear them and try to analyze."
The White House said that Putin initially approached Mr. Obama. After some small talk, the leaders made their way to a corner of the room for a conversation about Syria that officials said was free of acrimony.
Mr. Obama seconded that characterization. "The conversation I had with President Putin was on the margins of the [G-20] plenary session," he said. "It was a candid and constructive conversation...On Syria I said, 'Listen, I don't expect us to agree on this issue of chemical weapons use.' Although it is possible that after the U.N. inspectors' report it maybe more difficult for Mr. Putin to maintain his current position about the evidence."
"We both agree that the underlying conflict can only be resolved through a political transition," he added.
One thing that could unify the international response to Syria, Mr. Obama said, would be Assad's further use of chemical weapons. "Is it possible that Assad doubles down in the face of our action and uses chemical weapons more widely? I suppose anything's possible, but it wouldn't be wise," he said. "I think, at that point, mobilizing the international community would be easier, not harder."