Ohio Republican Sen. Rob Portman urged President Obama on Monday to wait until the new, Republican-controlled Congress takes office next year to work on immigration reform, instead of moving forward with executive action.

"It's crazy," Portman told Fox News' "America's Newsroom." "Here we've had this historic election, the American people have spoken… . They would like for us to work together and get stuff done.

"'It's just think it's a terrible way to start off what's supposed to be this fresh start where we have an opportunity with a Republican majority and a president of the other party."

Portman said Republicans and Democrats have "different approaches" to immigration policy, but the parties agree that the current system is “broken."

"There's some common ground here," he said. "Let's try to work together and get this done."

Portman also said a legal battle is sure to follow if Obama sidesteps Congress but using executive orders, which are expected to protect roughly 5 million illegal immigrants from deportation.

"We believe a lawsuit will be filed," he said. "I don't know if it will be resolved during his administration. That's the problem with these lawsuits. But it's illegal. … We believe it will be overturned at some point."

Still, Portman doesn’t think the potential showdown between the president and Capitol Hill Republicans during this lame duck, post-election congressional session will result in the sides failing to agree on a temporary budget, which would result in a partial government shutdown.

"No one wants to shut down government," he said. "The funding ends on December 11. If the president acts before (that), then I think there will be a lot of Republicans who will be frustrated with him and say, 'OK, we're not going to provide funding for him to execute this executive order.' That's not shutting down government, and I think that gets confused sometimes."