Obama will also address the nation Tuesday evening as new possibilities about a negotiated settlement with Syria seem likely to slow congressional action.

On Monday, Russia suggested an agreement under which Syria would give up control of its chemical weapons, and Syria indicated it could agree to this solution. That prompted Obama to acknowledge that this sort of agreement could allow Syria to dodge a U.S. attack.

“The situation in Syria is influx especially in the last few hours,” Casey said. “I am open to this diplomatic discussion however not without caution and not without skepticism.”

There are also new efforts within the United Nations to secure Syria's chemical weapons.

Casey said the only reason the new options were on the table was because of Obama’s “credible threat of force.”

Obama has asked for congressional support to use limited military strikes against Syrian President Bashar Assad, who is accused of using chemical weapons against his own people.

Last week, the Senate Foreign Relation Committee passed on a bipartisan 10-7 vote S.J.Res. 21, which would authorize a limited 60-day strike with the option to extend it an additional 30 days.

Senate leaders have delayed any further votes on this resolution until after Obama’s speech and possibly longer if a diplomatic deal becomes more promising.