President Obama fielded questions from reporters at news conference Friday at the G-20 summit in St. Petersburg, Russia. Syria, as expected, was the dominant topic of discussion. Here are the five biggest takeaways:

1. Obama will lean on the power of persuasion: The president said he will address the nation from the White House on Tuesday on the topic of Syria and his push for military action there in response to the alleged use of chemical weapons by the Syrian government against its own people. This will be a critical moment in the heated debate in Washington. Up until now, Secretary of State John Kerry has been the Obama administration's primary messenger on Syria, appearing on the Sunday shows, making announcements from the State Department and testifying before Congress. Tuesday's speech will be Obama's most direct and extended plea yet for military action, since he told the country six days ago that he would seek congressional approval. With more and more lawmakers expressing skepticism about military action in recent days, the question is whether Obama's high-profile address will change any minds. One of Obama's chief strengths is his rhetorical ability. Tuesday could be his last best chance to change minds of lawmakers and Americans on a broad scale.

2. What will Obama do if Congress doesn't sign off on military action? He still won't say. With lawmakers expressing deep skepticism about signing off on military action, the big question is what Obama will do if Congress doesn't pass a resolution to approve a strike. Asked repeatedly Friday, Obama wouldn't tip his hand. "I think it would be a mistake for me to jump the gun and speculate," he said. Obama has said he is not required to get the approval of Congress, and he's keeping alive the possibility that he would act even if they don't approve. Here's the issue: If Obama says whether or not he would proceed with an attack after a failed vote, he could change the way the vote is likely to play out in advance. He needs to make members feel that "yes" or "no" votes are consequential. If he says he is going to act anyway, it could give cover to lawmakers on the fence to vote "no," since action — which polls show is unpopular — would come even without their approval. If he says he will not act without Congress, Obama is leaving his next move entirely in the hands of lawmakers and limiting his flexibility.

3. Not a lot of new(s): Obama largely rehashed the argument that he, Kerry and other members of his administration have been making for the better part of the last 10 days — that Syria has committed a moral atrocity by gassing its own people and that that alone is a call to action. Obama also reiterated his insistence that words — his and those of the international community — have to mean something, and that not acting in Syria could serve as an encouragement to other rogue nations. But for members of Congress leaning against voting for the resolution or genuinely undecided about what to do, there wasn't much new in the way of an argument from Obama. Will he offer a new take — or a more aggressive one — when he speaks to the country Tuesday?

4. It's about much more than Syria: Obama repeatedly emphasized that while Syria was the focus of the moment, the decision before Congress was about much more than that. He insisted that it was about the future of global conflict and how the United States treats situations like Syria. That seemed to be some intentional stakes-raising by the president for the upcoming congressional vote on Syria; he painted it purposefully in broad terms and seemed to indicate that what was decided in Congress in the coming weeks would have a major impact on American foreign policy.

5. The Obama-Putin saga continues:  Obama called his chat with Russian President Vladimir Putin on the sidelines of the G-20 summit "a candid and constructive conversation." Obama said the two talked about Syria, but not about Edward Snowden. The meeting was a surprise development — which Putin notably announced before the White House did — since the White House had scrapped plans for a formal bilateral meeting amid a relationship that has been looking ever more tense. Where the relationship heads from here is unclear, but what is clear is that the two leaders do not see eye to eye on some key issues. And that doesn't look like it will change any time soon.