President Obama said he anticipates Congress will begin debating immigration reform in April and called on lawmakers to "finish the job" of crafting a bill that will create a pathway to citizenship for the nation's 11 million illegal immigrants.

But legislation may not move as fast, or go as far as he wants.

Obama made the remarks at a naturalization ceremony in the East Room of the White House for 28 civilians and members of the military, telling the group that the problems with America's immigration system are well-documented and the solutions have been proposed. "We've just got, at this point, to work up the political courage to do what's required to be done," he said.

Democratic leaders in the Senate recently announced they will unveil an immigration reform bill in April and will begin debating it by early summer.

According to those familiar with the Senate plan, which was authored by a bipartisan coalition of eight senators, it would establish a 13-year "path to citizenship" for the nation's 11 million illegal immigrants that would be contingent on adequate border security. The proposal would also create a guest-worker program for immigrants and a program to increase the number of work visas for foreigners.

But prospects for passage are far from assured, in part because many Republicans are wary of any bill that proposes a pathway to citizenship, which many in the GOP consider a form of amnesty for people who are living here illegally. The House, run by Republicans, is working on its own plan that is likely to be far less open to the idea of citizenship than the Senate bill.

Republicans will also have to grapple with two pending studies, by the conservative Heritage Foundation and Harvard University, that will address the high cost of immigration reform and its impact on low-wage earners, according to sources familiar with the reports.

Some Republicans have argued that providing legal status or citizenship for illegal immigrants would swamp the entitlement system, adding trillions to its cost and going against the GOP agenda of smaller and less expensive government.

"The Gang of Eight plan will absolutely break up any chance of reducing the size of government because it is going to add so many costs," said Roy Beck, president of NumbersUSA, a group that pushes for lower immigration levels. "Once they get into that kind of argument, it is going to make it increasingly hard for [Republicans] to go along."

But the Gang of Eight has some prominent GOP members, including Sen. Marco Rubio, a rising star in the Republican Party and a Tea Party favorite whose parents are Cuban immigrants. Last week, Sen. Rand Paul of Kentucky added his name to a growing list of Republicans who are favorable to providing a path to legal status for those who are here illegally.

Obama is hoping to pass a bill quickly, before his influence wanes as he moves into "lame duck" status. But Congress may not be able to meet his timeline. The Gang of Eight is still arguing over some of the details of its plan, including the size of a guest-worker program, and legislation could slow to a crawl in the House.

"The House is going to take its time," said Alex Nowrasteh, an immigration policy analyst at the Cato Institute's Center for Global Liberty and Prosperity. "They are going to do many hearings and a lot of debate on this issue. They are not going to ram it through."