That went nowhere, however. In fact, the U.N. estimates more than 100,000 people have been killed since the civil war began in 2011, in addition to more than 2 million becoming refugees and over 4 million being displaced within Syria.
Lakhdar Brahimi, the joint U.N.-Arab League envoy on Syria, expressed fresh hopes Friday that a peaceful, political solution to end the war could be reached. Kerry and Lavrov's talks were a big reason for his optimism, with Brahimi calling them "extremely important" -- not regarding chemical weapons, but for the peace process generally.
'A criminal act'
To keep up pressure on al-Assad, Obama on Friday described last month's chemical weapons attack a "criminal" act. Ban weighed in as well, saying the Syrian leader "has committed many crimes against humanity, and therefore I am sure there will be surely a process of accountability when everything is over."
U.S. officials say the mere existence of talks with Russia on the matter is progress, noting that such a prospect would not have been considered just a week ago due to Moscow's repeated efforts to block U.N. action against Syria.
Speaking to reporters Friday after he and Lavrov met with Brahimi, Kerry called the talks about Syria's chemical weapons "constructive."
"We are working hard to find common ground to be able to make that happen. And we discussed some of the homework that we both need to do," Kerry said.
Lavrov said Russia had promoted a peaceful solution to Syria's civil war, adding that the communique agreed to in last year's first round of peace talks involving all the parties had been "basically abandoned."
On chemical weapons, Lavrov said international officials had to work together "to design a road which would make sure that this issue is resolved quickly, professionally, as soon as practical."
Getting chemical weapons fraught with challenges
Even if all parties agree, weapons experts say the already major challenge of putting Syria's chemical stockpile under international control would be extremely difficult, if not impossible, amid an active civil war.
Syria this week acknowledged that it possesses chemical weapons and wants to join the global convention that bans them.
CNN's Nick Paton Walsh reports that the convention would become legally binding on Syria 30 days after it formally joins, meaning al-Assad's government would have to permit inspections at that time.
After another 30 days -- which would be 60 days from when it formally joined the convention -- Syria would have to declare its chemical weapons stockpiles.
On Thursday, al-Assad noted that joining the convention would give Syria the standard 30 days from compliance to declare its stockpiles, but Kerry responded by expressing concern about that long a time period, saying "we believe there is nothing standard about this process."
At the State Department on Friday, spokeswoman Marie Harf said that "verifying, accounting for securing and destroying a large stockpile of chemical weapons takes time," adding that "it's very difficult to do, particularly in an active war zone."
"If we keep forward momentum, if we believe there's a credible and verifiable plan on the table to do just that, we'll keep moving forward with that process, because resolving this issue diplomatically is certainly preferable to resolving it or to dealing with it with military action," Harf said.
Obama had tried to put together a NATO coalition to attack Syria, but the British Parliament voted against taking part, denying him a normally reliable ally. Other allies said they wanted U.N. authorization in the form of a Security Council resolution before they would join a coalition.
The president then asked Congress to authorize a military response in Syria but appeared in danger of losing that vote until the Russian proposal Monday provided a diplomatic opening.
In a speech to the nation 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 of the chemical attack.
Russian President Vladimir Putin responded with an op-ed posted Wednesday night on the New York Times' website, saying "there is every reason to believe" Syrian troops weren't responsible, while challenging Washington and the idea of "American exceptionalism."
His remarks provoked a strong reaction in the United States, with some U.S. politicians deeming them insulting and sickening. But rather than step back, Putin spokesman Dmitry Peskov fired back by claiming Washington was "unaccustomed (to) competition" in global matters and has "grown too used to patting everyone on the back patronizingly."
Other questions loom in Washington.
One has to do with the Syrian opposition, some of whom are already receiving U.S.-funded weapons and ammunition, according to a U.S. official. Yet there's some questions about the mix of moderates and Islamist extremists among the rebels, including some who are affiliated with al Qaeda.