Senior administration officials also outlined for the first time a timetable for a diplomatic resolution of the issue of the weapons, saying the U.S. will know within a few weeks whether a path is workable. The officials spoke only on condition of anonymity because they were not authorized to discuss the internal deliberations publicly.
U.N. inspectors prepared to turn in their own poison gas report this weekend, sure to be an important basis for any further action. Secretary-General Ban Ki-moon said Friday that he expected "an overwhelming report" that chemical weapons were indeed used on the outskirts of Damascus on Aug. 21.
Two U.N. diplomats, speaking on condition of anonymity because the time was not yet final, said Friday night that Ban was expected to brief the Security Council on the report Monday morning.
In Geneva, meanwhile, Kerry and Lavrov have disclosed little since their meetings began Thursday with Kerry's dismissal of Assad's offer to begin by turning over information, not weapons, starting weeks from now after signing an international convention.
A U.S. official said the talks were at a "pivotal point" and would continue Saturday morning. Some progress has been made on how to account for Syria's chemical weapons inventory, the official said, adding that the U.S. and Russia also had narrowed their differences over what each country believes to be the size of the Syrian stockpiles.
Kerry and Lavrov also met with U.N.-Arab League envoy Lakhdar Brahimi about the potential for a new peace conference in the Swiss city. Kerry said he, Lavrov and Brahimi agreed to meet around Sept. 28 on the sidelines of the annual U.N. General Assembly meetings in New York.
"We are committed to try to work together, beginning with this initiative on the chemical weapons, in hopes that those efforts could pay off and bring peace and stability to a war-torn part of the world," he said.
Kerry, flanked by Lavrov and Brahimi, told reporters after an hour-long meeting that the chances for a second peace conference in Geneva will require success first with the chemical weapons talks, which he said had been "constructive" so far.
"I will say on behalf of the United States that President Obama is deeply committed to a negotiated solution with respect to Syria, and we know that Russia is likewise. We are working hard to find the common ground to be able to make that happen," Kerry said.
Brahimi acknowledged the high stakes Friday. He told Kerry and Lavrov that their chemical weapons negotiation "is extremely important in itself and for itself, but it is also extremely important for us who are working with you on trying to bring together the Geneva conference successfully."
Kerry was traveling to Jerusalem Sunday to discuss the situation in Syria with Israeli Prime Minister Benjamin Netanyahu. He then planned to travel to Paris on Monday to meet with French Foreign Minister Laurent Fabius and British Foreign Secretary William Hague about the Syrian war. He will meet separately with Saudi Foreign Minister Saud al-Faisal.
After meeting Friday with the emir of Kuwait, Sheik Sabah Al Ahmed Al Sabah, Obama said the U.S. and Kuwait are agreed that the use of chemical weapons in Syria was "a criminal act."
"It is absolutely important for the international community to respond in not only deterring repeated use of chemical weapons but hopefully getting those chemical weapons outside of Syria," Obama said.
In Syria itself, U.S. officials said, Assad is continuing to move caches of chemical weapons and their delivery systems to different locations, even as he joins the chemical weapons convention and pledges to turn over his arsenal to international control at some point.
Assad has had the weapons distributed around the country in as many as four dozen sites for some time, and the U.S. has detected limited movements of the weapons in the last week or so, said two officials, speaking only on condition of anonymity because they weren't authorized to publicly discuss intelligence matters.
At the United Nations, Ban said Assad's government "has committed many crimes against humanity."
"Therefore, I'm sure that there will be surely the process of accountability when everything is over," he said in response to a question.
U.N. inspectors were sent to Syria to decide whether chemical weapons were used, but their mandate did not include assigning blame. The Obama administration says it has evidence that the Syrian government was behind the attack and that 1,429 people died. Some other estimates are lower, and the Syrian government has pointed to the rebels as the culprits. But the government also has expressed willingness to begin eliminating the weapons.
More than 100,000 people have been killed in two years of civil war marked by grisly reports of attacks on civilians. On Friday, the international group Human Rights Watch accused the Syrian government and militias fighting on its side of carrying out summary executions of at least 248 people in two towns in May. And the United Nation said it was allocating a record $50 million to help the millions of refugees from the war.
Russian and American weapons experts met several times Friday in Geneva to try to work out acceptable details for the expensive and difficult process of actually eliminating Syria's chemical weapons.
Lavrov said that Russia had supported the peace process from the start of the Syrian conflict and that he had discussed with Kerry and Brahimi the Geneva communique from the 2012 meeting on Syria and ways of preparing for a second conference.
"It is very unfortunate that for a long period the Geneva communique was basically abandoned," said Lavrov.
Salem Al Meslet, a senior member of the opposition Syrian National Coalition, said he was disappointed that the Kerry and Lavrov meeting wasn't about punishing Assad.
"They are leaving the murderer and concentrating on the weapons he was using," he said of Assad. "It is like stabbing somebody with a knife then they take the knife away and he is free."
Assad, in an interview with Russia's Rossiya-24 TV, said the Russian proposal for securing the weapons could work only if the U.S. halted threats of military action.
At a meeting in Kyrgyzstan on Friday, Russian President Vladimir Putin said that Syria's efforts have demonstrated its good faith. "I would like to voice hope that this will mark a serious step toward the settlement of the Syrian crisis," Putin said.
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Connie Cass reported from Washington. AP writers Lolita C. Baldor and Julie Pace in Washington and Maria Sanminiatelli in New York contributed to this report.
