Air Force One touched down outside Washington at 9:40 p.m. EDT and by 10:04 p.m. Obama, accompanied by press secretary Jay Carney and a handful of other staffers, had taken the Marine One shuttle to the White House South Lawn, officially ending his trip.
The president, wearing a dark suit and tie, waved to nearby reporters but had nothing to say to them as he walked into the White House.
Obama spent part of his time on his trans-Atlantic flight phoning members of Congress from both parties but no names were provided.
Earlier in the day in St. Petersburg, Russia, the G-20 leaders were meeting in plenary session when Putin approached Obama and the two moved to a corner of the room, sat down and spoke for 20-30 minutes.
Evidence shows the Syrian regime was responsible for the "horrific chemical attack" in August, several G-20 summit participants said in a statement.
The White House released a joint statement by leaders and representatives of Australia, Canada, France, Italy, Japan, Republic of Korea, Saudi Arabia, Spain, Turkey, the United Kingdom and the United States attending the summit that condemned the chemical weapons attack Aug. 21 in rebel-controlled suburbs of Damascus.
"The international norm against the use of chemical weapons is longstanding and universal. The use of chemical weapons anywhere diminishes the security of people everywhere. Left unchallenged, it increases the risk of further use and proliferation of these weapons," the statement said.
"We condemn in the strongest terms the horrific chemical weapons attack in the suburbs of Damascus on Aug. 21 that claimed the lives of so many men, women, and children," the statement said. "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."
During a news conference at the summit, Obama said he will take his case for a military response in Syria to the American people with an address Tuesday.
He said he and Putin -- who has backed Syria, Russia's long-time ally -- discussed the situation, noting that the two leaders agree on some issues while disagreeing on others.
Obama said he told Putin he didn't expect the two leaders to see eye to eye, "although it is possible that after the U.N. inspectors report it may be more difficult for Mr. Putin to maintain his current position."
"But we both agree that the underlying conflict can only be resolved by a political transition" that a delayed international forum in Geneva, Switzerland, sponsored by Russia and the United States needs to move forward.
"Even if we disagree on this important issue," Obama said, "we must remain together to urge all parties in conflict" to try to resolve it through political measures, not military ones.
The joint statement called 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."
It said its signers consistently supported a strong U.N. Security Council resolution on the situation, but recognized that the panel has been "paralyzed" and the world cannot wait.
"We support efforts undertaken by the United States and other countries to reinforce the prohibition on the use of chemical weapons," the statement said, noting the signing countries are committed to seeking a political solution.
During his news conference, Obama said he wasn't interested in a "long, drawn-out" presence in Syria, only enforcing international norms banning the use of chemical weapons.
Syrian President Bashar Assad must understand that "gassing innocent people ... delivering chemical weapon against children is not something we do."
"It's prohibited in active wars between countries. We certainly don't do it against kids. We've got to stand up for this principle," Obama said.
The U.S. State Department said Friday it withdrew non-emergency workers and families from the U.S. Embassy in Beirut. Lebanon, because of safety and security concerns in Lebanon.
"U.S. citizens living and working in Lebanon should understand that they accept risks in remaining and should carefully consider those risks," the department said in an alert posted on its website.
The alert noted the conflict in Syria resulted in "numerous security incidents between the border regions between Lebanon and Syria and coincides with an increasing number of security incidents around the country."
Another State Department alert said the department ordered the drawdown of non-emergency government personnel and their families from the U.S. Consulate General in Adana, Turkey, and alerted Americans traveling to or living in Turkey to the "potential for violence."
In St. Petersburg, Obama dismissed a report that the Pentagon was expanding its list of feasible Syria targets and may conduct airstrikes with France in addition to firing cruise missiles.
"That report is inaccurate," Obama said. "I'm not going to comment on operational issues that, you know, are sourced by some military official. One thing I've got a pretty clear idea about is what I talk with the chairman of the Joint Chiefs of Staff about. And what we have consistently talked about is something limited and proportional that would degrade Assad's capabilities."