He also tried to assure the public that involvement in Syria will be a "limited, proportional step."
"This is not Iraq, and this is not Afghanistan," Obama said.
He met with top lawmakers hours before he leaves on a three-day trip to Europe, with a visit to Sweden and a G-20 summit in Russia.
Lawmakers in both the Republican and Democratic parties called for changes in the president's requested legislation, insisting it be rewritten to restrict the type and duration of any military action.
Officials said the emerging Senate measure would receive a vote Wednesday in the Senate Foreign Relations Committee. Approval is likely.
In the Senate, the compromise was the work of Sens. Bob Menendez, the Democratic chairman of the Senate Foreign Relations Committee, and Bob Corker, the senior Republican on the panel. Their committee held a lengthy hearing during the day on Obama's request for congressional legislation in support of the military reprisal he wants.
The proposed measure would set a time limit of 60 days for any military action and says the president could extend that for 30 days more unless Congress has a vote of disapproval.
The measure also bars the use of U.S. ground troops for "combat operations."
The White House had no immediate reaction to the Senate measure, although Kerry, testifying earlier before the committee, signaled that the troop restriction was acceptable to the administration. "There's no problem in our having the language that has zero capacity for American troops on the ground," he said.
Kerry, one of three senior officials to make the case for military intervention at the hearing, had said earlier that he'd prefer not to have such language, hypothesizing the potential need for sending ground troops "in the event Syria imploded" or to prevent its chemical weapons cache from falling into the hands of a terrorist organization.
"President Obama is not asking America to go to war," Kerry said. He added, "This is not the time to be spectators to slaughter."
Obama said earlier in the day he was open to revisions in the relatively broad request the White House made over the weekend. He expressed confidence Congress would respond to his call for support and said Assad's action "poses a serious national security threat to the United States and to the region."
The U.S. says it has proof that the Assad regime is behind sarin gas attacks that Washington claims killed at least 1,429 people, including more than 400 children. The Britain-based Syrian Observatory for Human Rights, which collects information from a network of anti-regime activists, says it has so far only been able to confirm 502 dead.
The Obama administration argues that the United States must exert global leadership in retaliating for what apparently was the deadliest use of chemical weapons anywhere over the past 25 years.
Boehner's support is key, but opposition Republicans in Congress do not speak with one voice.
And after a decade of war in Iraq and Afghanistan, polls show most Americans opposed to any new military action overseas.
Democratic and Republican lawmakers alike were divided over whether to support military action against Syria, although it appeared the Obama administration's biggest concern was winning support among deeply conservative Republicans who have battled with the president on issue after issue.
Some lawmakers say Obama still hasn't presented good evidence that Assad's forces were responsible for the Aug. 21 attack. Others say he hasn't explained why intervening is in America's interest.
Those questions come a decade after the Bush administration badly misrepresented the case that Iraqi President Saddam Hussein possessed weapons of mass destruction.
The president met top lawmakers at the White House before embarking on an overseas trip to Sweden and Russia, leaving the principal lobbying at home for the next few days to Vice President Joe Biden and other members of his administration.
Kerry, Defense Secretary Chuck Hagel and Gen. Martin Dempsey, chairman of the Joint Chiefs of Staff, sat shoulder-to-shoulder at the Senate committee hearing.
A few hundred miles away, United Nations Secretary-General Ban Ki-moon urged caution. He said any punitive action against Syria could unleash more turmoil and bloodshed, and he advised that such strikes would be legal only in self-defense under the U.N. Charter or if approved by the organization's Security Council. Russia and China have repeatedly used their veto power in the council to block action against Assad.
Russia and China have repeatedly used their veto power in the council to block action against Assad.
Among major allies, only France has publicly offered to join the United States in a strike, although President Francois Hollande says he will await Congress' decision. The British House of Commons rejected a military strike last week.
In the Middle East, Israel and the U.S. conducted a joint missile test over the Mediterranean in a display of military might in the region.
House Republican Majority Leader Eric Cantor also said he would support Obama's call for military action against Syria.
Obama also won conditional support Monday from two of his fiercest foreign policy critics, Republican Sens. John McCain and Lindsey Graham.
The administration argues that the alleged sarin gas attack last month violated not only the international standard against using such weapons but also Obama's "red line," set more than a year ago, that such WMD use wouldn't be tolerated.
Obama said he believes he has the authority to undertake limited military action without congressional backing, but he has stated that the United States will be stronger if lawmakers grant their support.
Neither Obama nor his aides, however, has been willing to state what options would be left to him should Congress reject his call.
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Associated Press writers Bradley Klapper, David Espo and Nedra Pickler contributed to this report.
