Gregory Korte

USA TODAY

WASHINGTON — President Obama meets with his attorney general Monday to discuss his options for regulating guns, signalling that gun violence will be a top priority of his administration in the new year.

Calling the issue of gun violence "one piece of unfinished business" as he enters the last full year of his presidency, Obama said he gets too many letters "to sit around and do nothing." But anything Obama does by executive action is likely to be undone if a Republican moves into the White House in 2017.

The gun issue may dominate the White House agenda in the run-up to Obama's last State of the Union Address next week. Obama will participate in a televised town hall-style event Thursday on CNN called Guns in America. And on Friday, he'll mark the fifth anniversary of the 2011 Tucson shooting that killed six and wounded Rep. Gabrielle Giffords, who has since left Congress to found a gun control lobbying group that met with Obama personally last month.

Obama delivers his State of the Union Address to Congress on Jan. 12, a venue traditionally used to prod legislation from Congress and announce actions from the executive branch.

"The president has made clear the most impactful way to address the crisis of gun violence in our country is for Congress to pass some common sense gun safety measures," White House Deputy Press Secretary Eric Schultz told reporters in Honolulu, where Obama spent Christmas vacation. "But the president has also said he's fully aware of the unfortunate political realities in this Congress. That is why he has asked his team to scrub existing legal authorities to see if there's any additional action we can take administratively."

Schultz said that work would be completed soon. "The president has made clear he's not satisfied with where we are," he said.

The White House hasn't said what options the president is considering, but some of the most-discussed possibilities are likely to raise legal issues. The president can't re-write gun control legislation, but he can direct Attorney General Loretta Lynch to interpret and enforce those laws more aggressively.

For example, Obama has long decried the so-called "gun show loophole" that allows gun buyers to circumvent federal background checks by purchasing weapons at flea markets and collector's events, and could change regulations redefining whether those sellers should be required to conduct background checks.

In his weekly radio address on Friday, Obama acknowledged that any executive action would not stop mass shootings. "We know that we can’t stop every act of violence. But what if we tried to stop even one? What if Congress did something — anything — to protect our kids from gun violence?" he said.

As Obama returned from a two-week vacation in his native Hawaii Sunday, Republican presidential hopefuls were condemning the as-yet-announced actions as illegal.

"To use executive powers he doesn’t have is a pattern that is quite dangerous," former Florida governor Jeb Bush said on Fox News Sunday. New Jersey Gov. Chris Christie said Obama was acting like a "dictator" and said he would undo any executive actions not already overturned by the courts.

And at a rally in Biloxi, Miss., on Saturday, real estate mogul Donald Trump promised that if Obama signs executive actions on guns, he would "unsign that so fast" once he becomes president.