Republicans vowed to do everything in their power to block U.S. President Barack Obama's executive action on immigration aimed at protecting millions of undocumented migrants in the country from deportation.

The GOP has been all up in arms in recent weeks, with Oklahoma Sen. Tom Coburn even going so far as to imply the possibility of violence in the streets should Obama push through with unilateral action, which is expected to be announced on Thursday.

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Those opposed to the plan have called Obama "emperor" and accused him of taking unilateral action too far. As a Republican-controlled Senate prepares to take office in January, GOP lawmakers have warned Obama that his actions would not go unchallenged.

So far, Republicans have considered passing a spending-cap bill, filing a lawsuit to invalidate Obama's executive action, and stonewalling on future immigration policy, Fox News relayed.

Texas Sen. Ted Cruz on Wednesday also suggested retaliation by filibustering on Obama's executive and judicial nominees for as long as the "illegal amnesty" continues.

"Emperor" Obama has long-ignored the American people, said Michael Steel, GOP House Speaker John Boehner's spokesperson.

Pushing through with the amnesty plan - which the president acknowledged goes beyong his "Constitutional authority" - would reinforce his "legacy of lawlessness" and undermine chances of future Congressional action on the issue, among others, Steel said.

The administration, with backing from Democratic lawmakers, have argued that the GOP's failure to pass an immigration reform last year has forced Obama to take action to deal with the country's immigration problem.

A comprehensive bill on the issue was passed by the U.S. Senate in 2013 but has been delayed at the House of Representatives for months.

Obama is reportedly looking to grant more than four million undocumented immigrants with two-year reprieves under the Deferred Action for Childhood Arrivals, while another one million is to be offered similar protections through other means.

Administration officials told media earlier this week that while the provisions would not provide access to federal benefits such as Medicaid, health tax credits or food stamps, a number of immigrants will be eligible for work permits, Social Security cards and other state services. 

TagsBarack Obama, Republican, Senate, Congress, Democrat, politics, Deferred Action for Childhood Arrivals, DACA, Executive action on immigration reform, Obama immigration