McConnell, speaking with Fox News's Martha MacCallum, declined to say how he would vote on a potential resolution of disapproval, but predicted that it "wouldn't be without controversy" if the president declares a national emergency. McConnell, speaking with Fox News's Martha MacCallum, declined to say how he would vote on a potential resolution of disapproval, but predicted that it "wouldn't be without controversy" if the president declares a national emergency.

"I think there are different opinions about it, and if he goes that route we'll just hash it out," McConnell said, asked if thought Republicans would line up behind Trump if he declares a national emergency.

The Senate GOP leader added that Trump could "prevail" in a potential fight with Congress by vetoing a resolution of disapproval if it reaches his desk. The the resolution would initially only need to be able to garner a simple majority in both chambers, Democrats would then need two-thirds support in both chambers in order to override a veto.

"The president could win anyway by vetoing the bill and then trying to get enough votes to sustain it, so may ultimately be able to prevail on the national emergency alternative," McConnell said.

Though a group of lawmakers have until Feb. 15 to reach a deal on breaking the months-long stalemate over the U.S.-Mexico border wall, the president hasn't yet ruled out declaring a national emergency.

Without a deal the government could face it's second partial shutdown in as many months. McConnell told Fox News on Tuesday that "nothing good comes out of a government shutdown."

But declaring a national emergency has garnered fierce pushback among Senate Republicans, who worry that it will got bogged down in court and set a precedent for a future Democratic president to circumvent Congress.