President Obama predicted Tuesday that Congress will vote to authorize military action against Syria and said he is open to rewording the original resolution he sent Congress to approve.

“We have high confidence that Syria used, in an indiscriminate fashion, chemical weapons that killed thousands of people, including 400 children, and in direct violation of the international norm against using chemical weapons,” Obama told reporters before a meeting with members of Congress at the White House.

“That poses a serious national security threat to the United States and to the region, and as a consequence, Assad and Syria needs to be held accountable," he added.

Key lawmakers, including close Obama ally Sen. Patrick Leahy, D-Vt., have said that resolution the White House sent them over the weekend is too open-ended, and they have gone to work rewriting it.

Obama said he would work with Congress on the wording as long as it protects the mission of sending a “clear message” to the government of Bashar Assad and “degrades his capabilities to use chemical weapons, not just now but also in the future.”

He said he expects a “prompt vote” when Congress returns next week. Asked if he's confident that he will garner enough congressional votes to pass a resolution authorizing force, he said simply: “I am.”

In an apparent nod to some GOP hawks' concerns that a military strike should diminish Syria's ability to use chemical weapons on its citizens again, Obama said he envisioned a “limited” and “proportional” mission designed to “degrade” Assad's capability.

“This is a limited, proportional step that will send a clear message not only to the Assad regime, but also to other countries that may be interested in testing some of these international norms, that there are consequences,” he said. “It gives us the ability to degrade Assad’s capabilities when it comes to chemical weapons.”

Going further than he did over the weekend, Obama also said the military action is designed to strengthen the opposition but again stressed that he did not envision any boots on the ground.

“It also fits into a broader strategy that we have to make sure that we can bring about over time the kind of strengthening of the opposition and the diplomatic and economic and political pressure required so that ultimately we have a transition that can bring peace and stability not only to Syria but to the region,” he said.

The meeting included a variety of members of Congress, including the top two Republicans: House Speaker John Boehner, R-Ohio, and Senate Minority Leader Mitch McConnell, R-Ky.

Members of the Armed Services and Foreign Affairs committees also attended the meeting in the White House Cabinet Room.

In addition to the White House meeting, three key members of Obama's team are scheduled to testify before the Senate Foreign Relations Committee: Secretary of State John Kerry, Defense Secretary Chuck Hagel and Joint Chiefs Chairman Gen. Martin Dempsey.

Obama and Vice President Joe Biden huddled with the lawmakers just hours before the president leaves for a trip to Sweden and Russia that will consume the rest of the week.

After a stop in Stockholm, Obama heads to St. Petersburg, Russia, for a Group of 20 summit where he will face Russian President Vladimir Putin, his strongest opponent to military action in Syria. Syria will likely dominate the talks.

The White House early Tuesday also announced that Obama discussed the Syria situation Monday night with Japanese Prime Minister Shinzo Abe and shared a "grave concern" about the use of chemical weapons in Syria.

"The two leaders agreed that the use of chemical weapons is a serious violation of international norms and cannot be tolerated," the White House said in a statement. "They pledged to continue to consult closely on possible responses by the international community."