This story was updated around 1:59 p.m. EST: President Obama in a speech Thursday night is expected to lay out changes that would relax U.S. immigration policy, followed by an event in Las Vegas Friday, according to unnamed administration sources who spoke with CNBC. White House officials haven't publicly confirmed the trip or the timing of the executive orders.

Original story:

U.S. President Barack Obama has faced plenty of criticism this year from both sides of the aisle over his approach to immigration reform, which has remained in limbo. But after months of backtracking and delays, Obama is set to act unilaterally on immigration any day now -- and it looks like he may go big. Five million people in total may be shielded from deportation under one of the options  the president may choose. 

Unnamed White House sources who spoke with the New York Times and Fox News said the president is expected to expand deportation relief to undocumented family members of immigrants who are already legally in the U.S., a move that addresses many immigration advocates’ complaints that existing deportation policy jeopardizes family unity. His most-anticipated measure is a potential extension of relief to undocumented parents of U.S. citizens or lawful permanent residents who have lived in the U.S. for a certain number of years.  That protection would likely be very similar to the 2012 Deferred Action for Childhood Arrivals (DACA) program, which granted two-year renewable reprieves from deportation and work permits to certain undocumented immigrants who came to the U.S. as children.

While around 500,000 of the estimated 1.2 million eligible immigrants have received protection under DACA to date, extending that program to parents of U.S. citizens or permanent residents who have been in the U.S. for at least 10 years would cover around 2.5 million additional immigrants, according to estimates by the Migration Policy Institute. A more liberal program that would require only five years’ residence in the U.S. would cover up to 3.3 million immigrants.

The president is reportedly also considering extending that relief to undocumented parents of DACA recipients, which could bump up the number of protected immigrants by an additional 40,000 to 80,000, depending on the requirements for length of stay in the U.S. White House sources told Bloomberg News on Tuesday that the plan would likely not include parents of DACA recipients, however.

DACA itself may also be expanded: According to Fox News, which cited a “source close to the White House” last week, Obama could adjust some requirements to expand protections for childhood arrivals. Currently, those eligible for DACA must have arrived in the U.S. before June 2007 and have been under the age of 31 as of June 2012. Obama is reportedly mulling over changes that would move the cutoff date to June 2010 and shift the age requirement to cover those who entered the U.S. before the age of 16. 

If Obama takes the broadest option, it could mean that 5 million immigrants, including those currently eligible for DACA, could be shielded from deportation -- around 40 percent of the nation’s 11.7 million unauthorized immigrant population. It would certainly be Obama’s boldest move on immigration during his time as president, although it would still be a modest measure in the larger scheme of immigration reform. Even though undocumented immigrants would get temporary deportation relief and authorization to work in the U.S., they would still not have a pathway to legal status. By contrast, the comprehensive immigration bill passed in the Senate last year provided paths to legal status for some 8 million immigrants.

Obama may also heed the growing call of immigration reform advocates to make changes to the controversial Secure Communities program that partners local law enforcement with the Immigration and Customs Enforcement agency. Secure Communities has been at the heart of backlash against Obama’s deportation policies, with immigrants’ rights groups saying it has too often swept up low-priority immigrants -- those with strong ties to U.S. communities and clean or minor criminal records -- in the deportation net and widened mistrust between immigrants and local police.

It’s unclear what a revamp of Secure Communities might look like, but Obama has reiterated a call to focus deportations on those with serious criminal backgrounds. “We’re deporting people that shouldn’t be deported,” he said during an appearance on CBS’ "Face the Nation" last week. “We’re not deporting folks that are dangerous and need to be deported.”

Obama is also expected to expand green cards for high-skilled immigrant workers, a move that comes after weeks of meeting with business leaders lobbying for immigration reform over the summer. One proposal floated earlier this year included rolling over unused employment-based visas from previous years and making them available to current applicants to ease long wait times. The move could effectively free up an additional 250,000 green cards that went unused over the past 20 years.

Republican lawmakers have been warning for months that any unilateral action by the president on immigration would have dire consequences for the fate of comprehensive immigration reform in Congress, with some mulling a potential government shutdown over funding. Some House and Senate Republicans, however, have been privately discussing plans for conservative immigration bills, according to Politico. 

While early reports suggested Obama could announce the orders as early as Friday, White House officials have stayed mum on a potential timeline. Obama himself said he would act before the year’s end, and some Democrat lawmakers have suggested waiting until after Congress passes an omnibus budget deal before issuing the orders. White House Press Secretary Josh Earnest said Tuesday that the president was “nearing a decision” on the final executive orders.