Earlier this year, President Obama said if Syrian President Bashar Assad used chemical weapons against his own people that it would be crossing a “red line” where the U.S. would then get involved.

Coats was the first Republican senator on the Senate floor to speak about Obama’s request for congressional authorization to strike Syria. He accused Obama of trying to “defend his own credibility” after pledging U.S. support to the rebels fighting Assad’s regime.

Obama is expected to address the nation tomorrow evening in an address. Coats said Obama would need to lay out what the plan of attack is to the American people. He also said it would be important to know what comes next if limited air strikes against Assad don’t work. Coats said he would reserve judgement on the resolution until after Obama makes his case to the public.

Ahead of Coats’ comments, Senate Majority Leader Harry ReidHarry Mason ReidMcConnell not yet ready to change rules for Trump nominees The Hill's Morning Report — Sponsored by CVS Health — Trump’s love-hate relationship with the Senate Trump to press GOP on changing Senate rules MORE (D-Nev.) filed a motion to proceed to S. Res. 21, which passed on a bipartisan 10-7 vote in the Senate Foreign Relations Committee. 

The Senate is expected to vote on whether to proceed to a debate on the resolution on Wednesday. It is unclear whether the motion to debate the Syria resolution will garner the 60 votes needed to overcome a filibuster; many senators have come out in opposition to the move, while others remain undecided.

The resolution would authorize a limited 60-day strike with the option to extend it an additional 30 days. Sen. John McCainJohn Sidney McCainFor .2 billion, taxpayers should get more than Congress’s trial balloons Overnight Defense: Pompeo lays out new Iran terms | Pentagon hints at more aggressive posture against Iran | House, Senate move on defense bill Senate GOP urges Trump administration to work closely with Congress on NAFTA MORE (R-Ariz.) amended the resolution by inserting language that would call for the administration to change the military equation in the country to help end the conflict.