Fox News contributor Charles Krauthammer said potential action by President Barack Obama on immigration may be "an impeachable offense."

Fox News reported Wednesday Obama would announce the use of executive action on a 10-point immigration plan as early as next week. The New York Times confirmed the report, though a senior administration official told The Huffington Post Wednesday the president had yet to decide on immigration action.

"I believe it is an impeachable offense," Krauthammer told Fox News host Megyn Kelly Thursday evening. "If the circumstances were different, if we were at the beginning of a presidency, if we hadn't had years when the Congress has been supine and unresponsive at other grabs of their authority by the executive ... this idea of prosecutorial discretion is really a travesty."

Krauthammer also said an executive order on immigration would be a "flagrant assault on the Constitution."

Senate Majority Leader Harry Reid (D-Nev.) on Thursday urged Obama to wait until December to take action on immigration. Less than 24 hours earlier, the Congressional Progressive Caucus sent a memo to the president asking him to "do it now" because "there's urgency." Reid's request was prompted by the threat of a government shutdown by Congressional Republicans.

"We're going to fight the president tooth and nail if he continues down this path. This is the wrong way to govern," House Speaker John Boehner (R-Ohio) said Thursday. He added, "All of the options are on the table. We're having discussions with our members, and no decisions have been made as to how we will fight this if he proceeds."

But Senate Majority Leader-Elect Mitch McConnell (R-Ky.) said Thursday there would be no government shutdown.

“We will not be shutting the government down or threatening to default on the federal debt,” McConnell said.

In an interview Sunday, Obama said he would do what he could on immigration through executive action.

"It's not going to be everything that needs to get done. And it will take time to put that in place," Obama said.