Rep. Steve King (R-Iowa) said Wednesday that the Republican House may have no choice but to deny the government funding for 2015 if President Barack Obama goes ahead with plans to legalize millions of illegal immigrants.

According to King, “all bets are off” on a continuing spending bill for the government if Obama moves ahead on his own.

“If the president wields his pen and commits that unconstitutional act to legalize millions, I think that becomes something that is nearly political nuclear,” King added, according to the Des Moines Register. “I think the public would be mobilized and galvanized and that changes the dynamic of any continuing resolution and how we might deal with that.”

Barack Obama Steve King illegal immigration Congress

U.S. Rep. Steve King (R-Iowa) (center) is threatening to hold up funding for the government if President Barack Obama moves ahead without Congress on immigration. Alex Wong/Getty Images

Obama is said to be considering steps on his own to somehow allow five to six million illegal immigrants to stay in the country and even get work permits. This move would likely be billed as a way to expand the Deferred Action for Childhood Arrivals policy, which has spared hundreds of thousands of younger immigrants from deportation, and lets them work in the country as well.

Obama has said he would take some sort of step on immigration by the end of the summer. That timing could mean a decision from the White House just as Congress is dealing with a short-term government funding bill for fiscal year 2015.

King also said the inclusion of language that rolls back Obama’s immigration moves would be a requirement before he could support any spending bill.

While King doesn’t speak for every Republican, his strategy could find significant support among House Republicans who have routinely criticized Obama for working without Congress on a range of issues. Back in July, the House passed legislation allowing the Speaker John Boehner (R-Ohio) to bring a civil law suit against Obama over how he has implemented Obamacare.

At the White House Wednesday, spokesman Josh Earnest said Republicans shouldn’t be threatening a government shutdown over immigration.

“We would hope that Republicans wouldn’t do the same thing again, to shut down the government, over a common-sense, bipartisan effort to try to mitigate at least some of the worst problems that are caused by our broken immigration system,” Earnest said.

When asked whether the threat of a shutdown would make Obama think twice about acting on his own on immigration, Earnest said, “No, it won’t.”

Republicans continue to be on high alert for any sign that Obama is about to move unilaterally on immigration. On Wednesday, Sen. Jeff Sessions (R-Ala.) warned that giving legal status to millions would make it harder for U.S. citizens to find jobs, which would be “disastrous for struggling workers.”

“If implemented, the president’s new executive actions would functionally end what little remains of interior immigration enforcement, giving free license to every person in the world—here today or planning to come tomorrow—to violate our immigration laws with impunity,” Sessions said.