Republican lawmakers blasted the White House on the heels of a Fox News report that President Obama is planning to unveil a 10-part plan for overhauling U.S. immigration policy via executive action as early as next week – with one GOP leader warning there will be “an explosion” if the president moves too soon.

A source close to the White House told Fox News that Obama could announce as early as next Friday. The president's plans were contained in a draft proposal from a U.S. government agency – it includes a plan to suspend deportations for millions.

As Democratic lawmakers and immigrant advocacy groups urge Obama to act as soon as possible, Republicans bristled at the apparently looming announcement.

"He will make the issue absolutely toxic for a decade,” Rep. David Schweikert, R-Ariz., said Thursday.

One concern is that Obama would act before a Dec. 11 deadline for passing a new spending bill. Doing so could thrust the immigration debate into the budget process, with conservatives threatening to yank money from the immigration effort – and potentially triggering another showdown that could result in a partial government shutdown.

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Indeed, Rep. Matt Salmon, R-Ariz., already has gathered dozens of signatures on a letter calling for no funding for “the President’s reported intentions to create work permits and green cards for undocumented immigrants currently in the United States.”

House Appropriations Committee Chairman Hal Rogers, R-Ky., said Thursday if Obama acts before the spending bill is done, there will be an “explosion.”

Sen. Jeff Sessions, R-Ala., meanwhile, reiterated his concerns that the president would be acting outside the law.

“The president has no authority to do this. It's against the law,” he told Fox News.

The draft plan contains 10 initiatives that span everything from boosting border security to improving pay for immigration officers. But the most controversial pertain to the millions who could get a deportation reprieve under what is known as "deferred action."

The plan calls for expanding deferred action for illegal immigrants who came to the U.S. as children -- but also for the parents of U.S. citizens and legal permanent residents.

The latter could allow upwards of 4.5 million illegal immigrant adults with U.S.-born children to stay, according to estimates.

Sessions voiced concerns that illegal immigrants could simply fib in order to meet the criteria for the program. Further, he said millions more people would then be “entitled” to U.S. privileges including health care.

White House Press Secretary Josh Earnest, traveling with the president in Burma, stressed that the president “has not made a final decision at this point about exactly what will be included in the administrative steps that he will take.”

He would not specify the timing, but reiterated that Obama plans to make an announcement before the end of the year. “That should be an indication to you that the president is nearing a final decision,” he said.

Earnest also said that Obama would “retract” his executive actions if the House passes an immigration overhaul previously passed by the Senate.

The planning comes as immigrant advocates and Democratic lawmakers urge Obama to act.

Rep. Rubén Hinojosa, D-Texas, chairman of the Congressional Hispanic Caucus, said in a statement to Fox News Latino that they are urging the president to “go big and bold.”

He said “White House senior officials have assured our Caucus that the President will announce executive actions before the end of the holiday season.”

Angela Maria Kelley, vice president for immigration policy at the Center for American Progress, touted executive action as a "tried and true component of immigration policy used by 11 presidents, 39 times in the last 60 years."

She said for many undocumented immigrants who have been here for years, "there is no line for people to get into."

Fox News’ Lucas Tomlinson and Chad Pergram contributed to this report.