President Barack Obama will unveil his long-awaited plan to overhaul U.S. immigration policy Thursday night, granting relief from deportation to millions of undocumented immigrants and setting off an explosive showdown with Republicans.

In a minute-long Facebook video, President Obama said he will address the nation Thursday night.

Frustrated by years of congressional inaction on immigration reform, the president said he is now prepared to act unilaterally.

"Unfortunately, Washington has allowed the problem to fester for too long. And so what I'm going to be laying out is the things that I can do with my lawful authority as president to make the system work better," Obama said.

Obama's executive orders are expected to remove the threat of deportation for as many as 5 million of the estimated 11 million people living illegally in the U.S. The reprieve from deportation would cover some parents of U.S. citizens and legal permanent residents.

This move could impact 100,000 undocumented immigrants living on Long Island.

Luis Valenzuela, of the Long Island Immigrant Alliance, says the fear of deportation is especially stressful for families with a combination of legal and undocumented members.

Republicans have attacked Obama's planned unilateral orders as an abuse of executive authority. Rep. Peter King (R - Seaford) said, "By issuing an executive order of this magnitude, President Obama is violating the letter and spirit of the Constitution and is guilty of an arrogant overreach of power."

Some conservative Republicans are threatening a government shutdown.

Others say the president will poison his relations with the new Republican-controlled Congress if he makes good on his promise to act on immigration reform before the end of the year.