President Obama is announcing executive orders on gun control, but how does that work? Here's a look at how the White House, Congress and the Supreme Court have roles — and limitations — in executive orders. (Julie Percha,Jackie Kucinich,Rebecca Schatz/The Washington Post)

The Obama administration on Monday unveiled a series of new executive actions aimed at reducing gun violence and making some political headway on one of the most frustrating policy areas of President Obama’s tenure.

The package, which Obama plans to announce Tuesday, includes 10 separate provisions, White House officials said. One key provision would require more gun sellers — especially those who do business on the Internet and at gun shows — to be licensed and would force them to conduct background checks on potential buyers. Obama would devote $500 million more in federal funds to treating mental illness — a move that could require congressional approval — and require that firearms lost in transit between a manufacturer and a seller be reported to federal authorities.

At the president’s direction, the FBI will begin hiring more than 230 additional examiners and other personnel to help process new background checks 24 hours a day, seven days a week. Also, the Bureau of Alcohol, Tobacco, Firearms and Explosives has established a new investigation center to keep track of illegal gun trafficking online and will devote $4 million and additional personnel to enhance the National Integrated Ballistics Information Network.

“The gun lobby may be holding Congress hostage, but they can’t hold America hostage. We can’t accept this carnage in our communities,” Obama said in a Twitter message Monday evening, referring to the National Rifle Association.

The president is scheduled to talk about his new policies in the East Room on Tuesday, and two days later he will participate in a town hall at George Mason University that will be televised on CNN.

President Obama formally announced a set of executive orders on gun control on Jan.5. Here is what you need to know about how the regulations tighten gun sales and expand background checks. (Claritza Jimenez/The Washington Post)

Even before Obama’s official announcement, however, Republicans in Congress and on the campaign trail blasted the actions, and some gun rights advocates threatened to challenge them in court.

House Speaker Paul D. Ryan (R-Wis.) issued a statement Monday saying that even without knowing the plan’s details, he thinks “the president is at minimum subverting the legislative branch, and potentially overturning its will. . . . This is a dangerous level of executive overreach, and the country will not stand for it.”

Senate Judiciary Committee Chairman Charles E. Grassley (R-Iowa) said Monday that he and his colleagues would “be taking a deep look at the president’s proposals, with an eye toward ensuring that the Second Amendment is preserved.”

Although modest compared with any legislation that Congress could adopt, Obama’s executive actions will affect areas such as how the federal government might leverage its purchasing power to advance “safe gun” technology as well as what information federal and local law enforcement will share on individuals who are illegally trying to purchase weapons.

The president, who went over the initiatives in the Oval Office on Monday with administration officials including Attorney General Loretta E. Lynch and FBI Director James B. Comey, said inaction by Congress in the wake of several high-profile mass shootings and other gun-related violence justified his decision.

“And although it is my strong belief that for us to get our complete arm around the problem Congress needs to act, what I asked my team to do is to see what more we could do to strengthen our enforcement” to curb illegal gun sales, Obama said in brief remarks to reporters after the meeting. “And the good news is, is that these are not only recommendations that are well within my legal authority and the executive branch, but they’re also ones that the overwhelming majority of the American people, including gun owners, support and believe in.”

One of the main provisions is new federal guidance requiring some occasional gun sellers to get licenses from ATF and conduct background checks on potential buyers. Rather than set a single threshold for what triggers this licensing requirement, it will be based on a mix of business activities such as whether the seller processes credit cards, rents tables at gun shows and has formal business cards.

In some cases, officials said, a person who sells a single gun could be required to get a license, though in other cases, sellers who are classified as hobbyists or collectors could still qualify for exemptions.

A recent survey of more than 2,000 gun owners by Harvard University researchers found that of those who purchased their most recent firearm, about a third did not undergo a background check.

In a conference call with reporters, Lynch said the administration could not estimate how many more people would be affected by the new licensing provisions. She said gun sales are increasingly moving online and into largely unregulated areas of the “dark Web” where illicit activities take place in hidden transactions.

“The industry is shifting and growing,” she said. “If it does stop one act of violence, this will be worth it.”

Other aspects of the president’s plan aim to bolster the FBI’s background-check system, including a push by the U.S. Digital Service to modernize its processing operations and a proposal to add 200 new ATF agents and investigators to bolster enforcement.

Obama will instruct federal agencies, which collectively represent the nation’s largest firearms purchaser, to “explore potential ways” to promote technology that would prevent the accidental discharge or unauthorized use of a gun, according to White House officials.

Another measure will require federally licensed gun dealers to report any lost and stolen guns to the National Crime Information Center. Over the past five years, according to the White House, an average of 1,333 guns recovered in criminal investigations each year were traced back to a seller who claimed the weapon was missing but did not report it to authorities.

“This is a broad set of actions that tackles a variety of the issues related to gun violence,” said Arkadi Gerney, a senior fellow at the liberal think tank Center for American Progress, “and in combination it represents a comprehensive effort to strengthen the laws we already have on the books.”

Although the number of mass shootings in the United States has risen in recent years, overall gun violence is at lower levels than in previous decades. Obama, however, emphasized that gun deaths in the United States remain higher than in other developed countries in almost every category, including suicides.

“And although we have to be very clear that this is not going to solve every violent crime in this country, it’s not going to prevent every mass shooting, it’s not going to keep every gun out of the hands of a criminal,” he said, “it will potentially save lives and spare families the pain and the extraordinary loss they’ve suffered as a consequence of a firearm getting in the hands of the wrong people.”

Obama’s determination to act in his final year in office comes after he pledged last fall to make guns a political issue after a gunman killed 10 and wounded seven others at a community college in Roseburg, Ore. The president has made public statements after at least 16 mass shootings during his presidency, including the killing of 14 people in San Bernardino, Calif., last month by a married couple, reportedly inspired by the Islamic State.

His administration failed to persuade lawmakers to approve tighter legislative controls on gun sales in 2013, in the wake of the December 2012 killings of 20 children at an elementary school in Newtown, Conn. After that, the president issued a series of 23 executive actions to tighten controls and increase safety preparations, and he added two more in subsequent years.

But the White House was moved to act again after the shootings at Umpqua Community College in Roseburg. Administration lawyers have spent months reviewing various proposals to ensure that the redefinition of what it means to be “engaged in the business” of selling firearms can withstand legal challenges.

“The law has long been fuzzy, and the transition of gun sales away from brick-and-mortar stores to gun shows and the Internet requires the administration to clarify the definition,” said Sen. Chris Murphy (D-Conn.), who met with Obama along with other lawmakers on Monday. “By forcing more dealers at gun shows to run background checks, there will be less criminals that buy guns and less illegal guns sold on the streets of America.”

Dan Gross, president of the Brady Campaign to Prevent Gun Violence, said in an interview Monday that it was “a historic step” that would subject thousands of gun sales each day to stricter scrutiny.

One dilemma for the Obama administration would be that a legal fight could put the executive actions on hold as a court deliberates, potentially dragging out the process until Obama leaves office next January. The president’s executive actions to defer the deportations of millions of undocumented immigrants, announced in 2014, have been held up in a legal battle that could head to the Supreme Court this spring.

“I wouldn’t be surprised if they try,” White House press secretary Josh Earnest said when asked whether gun rights advocates would mount a legal challenge, “but the arguments we could mobilize in a court of law would be powerful and persuasive.”

Obama’s plans already have resonated on the presidential campaign.

Every GOP presidential candidate who has spoken about Obama’s potential actions has vowed to reverse the executive order if elected president, underscoring the fragility of any initiative that has not won congressional approval.

Speaking at a Christian bookstore Monday in Boone, Iowa, Sen. Ted Cruz (R-Tex.) called the idea “illegal and unconstitutional,” a theme echoed by several of his colleagues in recent days.

On Sunday, Sen. Marco Rubio (R-Fla.) told an audience in Raymond, N.H., that Obama “has waged war on the Constitution.”

“You can pass all the gun laws in the world that you want,” he said. “It will not stop the criminals.”

But Democratic presidential front-runner Hillary Clinton applauded Obama during a campaign stop in Iowa on Monday, saying she would go even further as president, and White House officials remained confident that public opinion is on their side.

“We are dedicated to doing everything we can to get guns out of the wrong hands,” said senior Obama adviser Valerie Jarrett. “We’ve talked to so many gun owners who don’t believe the NRA represents their views.”

Anne Gearan and Katie Zezima in Iowa contributed to this report.