The exact number will vary depending on last-minute tweaks to the plan, which was described by an administration official and two outside advocates who were briefed on deliberations and spoke on the condition of anonymity.
"Everybody agrees that our immigration system is broken," Obama said in a video posted on Facebook announcing his plan to speak Thursday. "Unfortunately, Washington has allowed the problems to fester for too long. So, what I'm going to be laying out is some things I can do with my lawful authority as president to make the system work better."
The announcement follows months of back-and-forth involving Obama, immigration overhaul advocates and members of
For months, Obama has said he was holding off taking executive action in the hopes that the Republican-led House would follow the Democratic-led
But with his party's sweeping losses in that election and
The administration refused to release specifics of the plan Wednesday, but it has already riled critics who question whether Obama is overstepping his executive authority by ordering a change that could directly affect millions of people.
A spokesman for House Speaker
Obama said in his Facebook video that he still hoped to work out a solution with Congress, but that only added fuel to the fiery criticism building on Capitol Hill.
"He's trying to pick a bar fight," Republican Rep.
"I used to do political campaigns. I know when the aim is to divide," added Cole, a former pollster. "That's the game he's playing. He's not trying to come to an agreement."
Advisors to Obama argue that he isn't overstepping the bounds of his executive authority. Every president since Eisenhower has used the power of the executive branch to tweak U.S. immigration policy, White House Press Secretary Josh Earnest said Wednesday.
Obama's move, he said, would be "consistent with actions taken by presidents of both parties to deal with the immigration system."
Under the plan, the White House would halt the deportation of millions of parents of U.S. citizens and long-term permanent residents, according to those briefed on the plan.
That program, to be rolled out in phases over its first year in order to prevent a crush of applications, would allow immigrants who qualify to pay a fee and submit to a background check and be given a temporary reprieve from deportation.
The number of people eligible will depend on residency requirements. If the guidelines call for five years of living in the U.S., 3.3 million people could be eligible to be protected from deportation. If the requirement is set at 10 years, 2.5 million would be eligible.
A small but significant option that was taken off the table was a change to policy that would have protected parents of children who received work permits through the Deferred Action for Childhood Arrivals program. Such a change was seen as too difficult to defend legally and politically.
Keeping out that group of parents could reduce the number of people eligible for assistance by about 100,000, according to figures from the Migration Policy Institute, a Washington-based think tank.
"We were disappointed with that," said Gustavo Torres, executive director of CASA de Maryland, an advocacy group. "All of us are very clear this is a step in the right direction, what the president is doing. We celebrate that. But that is not enough. We're going to keep fighting."
Obama created the deferred action program two years ago, allowing more than 580,000 people who were brought to the U.S. illegally as children to be protected from deportation for two years. They can seek extensions.
Another possible modification Obama may announce, a change to the deferred action program's age limit, could affect hundreds of thousands more people in the country illegally.
"It will be a mixed-emotions day," said Lorella Praeli, a policy director for United We Dream, an advocacy organization that pushes for protections for people brought to the U.S. illegally as children, as well as their families.
Obama is also expected to allow several hundred thousand spouses of U.S. citizens to more easily apply for waivers to a policy that would keep them out of the country and away from their family members before they could get legal status to stay in the U.S.
The Department of Homeland Security has also revamped instructions to immigration officers that boosts the number of people considered low priorities for deportation. Depending on the changes, this could protect an additional 200,000 to half a million people from being deported over the next 10 years.
Obama's plan may also make it easier for foreigners on work visas to apply for long-term permanent residency. Workers from other countries could be allowed to apply for green cards and work in the U.S. while their applications are being reviewed.
Even with the executive order ready to go, one White House official said the president was ready to tear it up if Congress will take action.
Democrats didn't seem to be holding out hope.
"If the House votes on our bipartisan bill, the discussion about executive action would be made moot," said Sen.
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