Senators: Iran fight could make ISIS debate more difficult

Senators on Tuesday said acrimony between Republicans and Democrats over Iran made reaching an authorization for military force against the Islamic State in Iraq and Syria (ISIS) a little more difficult. 

Forty-seven Senate Republicans sent an open letter to directly to Iran this week, warning that any deal negotiated to rollback its nuclear program might not last beyond President Obama, outraging Democrats and the White House. 

However, reaching an authorization for the use of military force (AUMF) will take bipartisanship, and both sides already disagree on how it should be worded, noted Sen. Jeff FlakeJeffrey (Jeff) Lane FlakeThe Hill's Morning Report — Trump eyes wall money options as shutdown hits 21 days Poll: Sanders most popular senator, Flake least CBS News in talks to hire Flake: report MORE (R-Ariz.). 

"It's a difficult environment. There's a lot of animosity, obviously, and that has manifested in a lot of these issues, but these are too important to let divide us," he added.

But he added, "I think we can get there, I hope we do. Our allies and our enemies need to know that we speak with one voice."

Sen. Bill NelsonClarence (Bill) William NelsonFlorida lawmaker diagnosed with pancreatic cancer Rick Scott threw party at Florida governor’s mansion after DeSantis and family had moved in: report Restoration of voting rights by felons marks shift in Florida MORE (D-Fla.) was less sanguine.

"When 47 Republican senators try to cut the legs out from under the president and negotiations that are proceeding now in Geneva -- I was flabbergasted and if that can happen in these days, then I can't predict anything with the AUMF," he said.

Nelson said he was "absolutely appalled and saddened by" partisanship being injected into foreign policy and national security.

"What it sends is a message  to the rest of the world is that we are not united when these kinds of letters are being written," he said. 

The Senate Foreign Relations Committee is scheduled to question Secretary of Defense Ash Carter, Secretary of State John KerryJohn Forbes KerrySyria too complex to make decisions in 280 characters … even for a president Kerry to Trump: Forget 'fictional' border crisis, declare emergency for climate Russia's next moves in Venezuela should be closely monitored MORE, and Chairman of the Joint Chiefs of Staff Gen. Martin Dempsey on Wednesday morning as part of its efforts to craft an AUMF. 

Sen. Susan CollinsSusan Margaret CollinsSenators restart shutdown talks — and quickly hit roadblocks TSA absences raise stakes in shutdown fight Don't underestimate the power of nationwide outrage born from financial desperation MORE (R-Maine) said it's difficult to predict whether there would be an AUMF reached. 

"It has not resonated very well with people on either side of the aisle for totally different reasons so I'm not sure what the outcomes could be," she said.