Top U.S. lawmakers from both parties say they will support President Barack Obama in a military intervention against Syria when the issue comes to a vote as early as next week.
U.S. House Speaker John Boehner and House Minority Leader Nancy Pelosi made the comments after a White House meeting with Mr. Obama on Tuesday.
Boehner, leader of the Republican party in the House of Representatives, says the United States has the capability to stop Syrian President Bashar al-Assad and must send a warning to other countries that the use of chemical weapons will not be tolerated.
Nancy Pelosi, who leads Mr. Obama's Democratic Party in the House, said Syria's use of chemical weapons was outside of the "circle of civilized behavior." She said the United States must respond.
The Syrian government has denied chemical weapons use by the military.
Heading into the session, Mr. Obama said he was confident he could work with Congress to get a resolution authorizing military action.
He said he was asking Congress to approve a "proportional, limited" military response that would send a "clear message" to Mr. Assad's regime and any other country interested in "testing international norms."
"We recognize that there are certain weapons that when used can not only end up resulting in grotesque deaths but also can end up being transmitted to non-state actors, can pose a risk to allies and friends of ours, like Israel, like Jordan, like Turkey."
He also said the U.S. had a "broader strategy" that involves upgrading the capabilities of the Syrian opposition.
The meeting began a day of intense outreach to the Congress, including a scheduled appearance before the Senate Foreign Relations Committee by Secretary of State John Kerry, Defense Secretary Chuck Hagel and the Chairman of the Joint Chiefs of Staff General Martin Dempsey.
Senate Intelligence Committee chairwoman Dianne Feinstein, a Democrat, said before that hearing she is fully supportive of Mr. Obama's intended action.
The White House says Mr. Obama and Japan's Prime Minister Shinzo Abe discussed their "grave concern" about Syria's alleged use of chemical weapons during a phone call late Monday. The White House says the two leaders agreed that any use of chemical weapons is a "serious violation of international norms" and cannot be tolerated.
French President Francois Hollande said he will wait to see if Mr. Obama receives support from Congress before deciding on a French role in any military intervention. France, earlier, voiced support for military strikes against the Syrian government.
U.N. Secretary-General Ban Ki-moon scheduled a briefing later Tuesday for members of the Security Council.
Mr. Ban has met with the head of a U.N. inspection team that was in Syria last week collecting samples from last month's suspected chemical attack near Damascus, which killed at least 1,400 people. The samples were sent to labs on Monday for analysis.
Mr. Assad denies his military was responsible for the use of chemical weapons, saying the United States and France have no proof to back up their allegations.