While Kerry was in Geneva, Obama met with the rest of his Cabinet on Thursday and wished his absent secretary well.
"I am hopeful that the discussions that Secretary Kerry has with Foreign Minister Lavrov as well as some of the other players in this can yield a concrete result," Obama told reporters. "And I know that he is going to working very hard over the next several days to see what the possibilities are there."
Former U.S. Defense Secretary William Cohen told CNN on Thursday that Kerry will have his hands full with Lavrov, whom Cohen described as "very, very skilled," "bright," "articulate" and "a very tough negotiator."
Thursday's initial session revealed some of the dynamic between Kerry and Lavrov.
In their opening statements, Lavrov spoke first with mostly technical comments and then Kerry followed with longer and more forceful remarks. When he finished, Lavrov asked to respond and said he hadn't come "prepared with the extended political statement," adding that "diplomacy likes silence."
Kerry then asked the translator to repeat Lavrov's final comment, but when that didn't happen, Lavrov tried to assure Kerry there was no problem.
"You want me to take your word for it? It's a little early for that," Kerry said, smiling, as the two men shook hands for the cameras.
In some potential good news for Obama, French Foreign Minister Laurent Fabius said Thursday that a U.N. report on the August attack in Syria will "probably" be published on Monday, and that there will "certainly be indications" pointing to the origin of the attack.
France and other U.S. allies have said they want any international response on Syria to come under U.N. auspices, and the report by inspectors who traveled to the site of the attack would be a first step toward generating support for a Security Council resolution.
Obama makes case for action
The president insists he has the authority to attack Syria without congressional approval, but says he decided to seek the support of legislators for the sake of national unity.
In a speech Tuesday night, Obama made moral and strategic arguments for taking action on Syria, challenging Congress and the American public to look at video footage of victims and saying that letting al-Assad get away with it would harm the security of the United States and its allies.
Opponents of a U.S. military strike argue that it could lead to another quagmire in someone else's civil war, and that Obama's proposal for limited strikes would fail to achieve the objective of eliminating the threat of Syria's chemical weapons.
Russian President Vladimir Putin injected himself into the American debate with an opinion piece first published late Wednesday on the New York Times website that argued against U.S. military intervention in Syria and implicitly criticized Obama.
The White House shrugged off Putin's jabs at Obama as "irrelevant," arguing that Russia's diplomatic intervention over Syria's chemical weapons meant that Putin now was "fully invested" in removing them from al-Assad's control.
Meanwhile, a U.S. official told CNN that CIA-funded weapons have begun flowing to Syrian rebels, as pledged by the administration in June.
The artillery described as light weapons, some anti-tank weapons and ammunition are not American-made, but are funded and organized by the CIA. They started to reach rebels about two weeks ago, the official said.
Gen. Salim Idriss, the head of the Free Syrian Army, told CNN's Christian Amanpour on Thursday that U.S. aid was reaching the rebels, though he didn't detail whether that support includes weapons.
"We are getting now a lot of support from our American friends, but I can't talk in detail about all kinds of the support," Idriss said.
Congress approved supplying weapons to the rebels after the administration asserted earlier this year that the al-Assad regime had used chemical weapons on a small scale.
Before that, Obama had rejected calls by his national security team and members of Congress to increase direct military aid to the rebels.
Those pushing for arming the rebels argue such a step would counter Russian weapons supplied to al-Assad's forces and strengthen the hand of moderate members of the Syrian opposition, making them less reliant on well-armed Islamic extremist elements within their ranks.
But a senior U.S. military official has said, "we do not see a clear division between moderates and extremists," making it hard to back the opposition without supporting extremist elements as well.
While one U.S. official says "only a minority are extremist" -- a reference to rebel fighters tied to the al Qaeda-linked al-Nusra Front -- U.S. officials familiar with intelligence assessments say many more rebel fighters than belong to that group may want to establish an Islamic state in Syria.
On the other side of the bloody war, al-Assad's forces are getting support from at least 2,000 members of Hezbollah -- a pro-Syrian group based in Lebanon that the United States has designed as a terrorist organization -- U.S. officials estimate.