Some immigrants covered under the executive action announced by President Barack Obama on Nov. 20 may be able to apply for deportation relief and work permits as early as mid-February.

Those eligible for the expanded Deferred Action for Childhood Arrivals, known as DACA, will be first up, Citizenship and Immigration Services Director Leon Rodriguez said. Parents of U.S. citizens and legal resident children will have to wait till May.

"We are very confident that this is completely legal, and it is going to be carried out," said Cecilia Muñoz, Obama's chief domestic policy adviser, according to NBC News.

The administration's measures will allow roughly 45 percent of undocumented immigrants to at least temporarily remain and work in the United States.

Many Republicans staunchly oppose the executive action, and 24 states are suing the president over his decision.

U.S. District Judge Andrew Hanen, the federal judge who will hear the states' challenge, has in the past been critical of Obama's immigration policies. Last year, he accused them of "engaging in a criminal conspiracy for returning young immigrants caught at the border to their families living in the United States." Hanen was appointed by then-President George W. Bush in 2002.

House Speaker John Boehner, meanwhile, on Thursday vowed that Republicans would mount a "direct challenge" to Obama's immigration orders next month. GOP congressmen attached language targeting the orders to the omnibus spending resolution passed Friday.

"(The) responsible bill to keep the government running and address the American people's priorities ... puts us on track to save taxpayers more than $2.1 trillion while protecting jobs and supporting our national defense," Boehner said. "(But) we are setting up a direct challenge to the president's unilateral actions on immigration next month, when there will be new Republican majorities in both chambers. We'll take this fight to the president."

Americans disapprove, 51 percent to 41 percent, of Obama's executive action on immigration, according to Gallup. Latinos, however, overwhelmingly approve the measure, with 64 percent in favor and 28 percent opposed.