U.S. President Joe Biden, declaring gun violence "a blemish on our character as a nation," on Thursday ordered tighter regulation of some weapons and pressed Congress to renew the country's long-expired ban on assault weapons.

"Gun violence in this country is an epidemic," Biden told a the White House audience of lawmakers and citizens touched by gun violence. "And it's an international embarrassment."

He said that as the number of mass shootings mounts, lawmakers in Congress have "offered plenty of thoughts and prayers ... but they have passed not a single new federal law to reduce gun violence. Enough prayers; time for some action."

King Soopers employees are led away from an active shooter at the King Soopers grocery store in Boulder, Colorado, March 22, 2021. Police say 10 people were killed in the shooting, including a police officer.

Biden offered his proposals after several high-profile mass killings, including gun attacks that in a week's time killed eight people at spas in the Atlanta, Georgia, area in the southern United States and 10 more at a grocery store in Boulder, Colorado, in the western part of the country.

Biden said that in the time between the two incidents, which drew nationwide television coverage, another 850 less publicized shootings killed 250 people and injured 500.

"This is an epidemic, for God's sake!" Biden said. "It has to stop."

Biden directed the Justice Department to issue a proposed rule to "stop the proliferation" of what law enforcement officials call "ghost guns" - handmade or self-assembled firearms that don't have serial numbers, making it difficult for police to track their owners when the weapons are used to commit crimes.

Some of the guns can be fabricated in a half-hour using kits and parts purchased online.

Another of Biden's proposed rules would target stabilizing braces for pistols, which give shooters more accuracy and help to manage recoil as they position them on their shoulders before firing. Police say such a weapon, effectively a short-barreled rifle, was used in the Colorado mass killing.

Under Biden's proposal, the White House said, the weapons would be covered by regulations in the National Firearms Act, which would require registration.

U.S. President Joe Biden listens as Attorney General Merrick Garland speaks about executive actions on gun violence prevention in the Rose Garden at the White House, April 8, 2021.

Attorney General Merrick Garland, speaking after Biden, said the Justice Department is planning to issue a model of what are known as "red flag" laws that give family members and law enforcement the ability to petition a court to temporarily restrict someone deemed to be a danger to themselves or others from accessing guns. The model is intended to give individual states a starting point for enacting their own laws.

The new efforts include an annual report on firearms trafficking, and a set of community violence interventions.

Democratic Party lawmakers have long called for tighter gun regulations while Republicans have voiced their ardent support for Second Amendment gun ownership rights.

Biden said his plans do not impinge on the rights of Americans under the Second Amendment of the U.S. Constitution, which guarantees the right to own a gun.

He said, however, "There is much more Congress can do."

Lawmakers have repeatedly talked about gun violence but failed to agree on measures to curb it. The U.S. banned the sale of assault weapons from 1994 to 2004, but the law was not renewed when it expired.

"It saved lives," Biden said of the assault weapons ban. "Nobody needs a weapon that fires 100 rounds."

FILE - In this September 25, 2019, file photo, David Chipman, Giffords Law Center senior policy adviser, speaks at a House Judiciary Committee hearing on assault weapons, on Capitol Hill in Washington.

Biden said he is planning to nominate David Chipman, a former federal firearms agent and adviser at the gun control group Giffords, to lead the U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives.

Chipman was a 25-year agent at the agency where he took part in the investigations of bombings at New York's World Trade Center and a federal building in Oklahoma City in the 1990s.

Chipman is likely to be sharply questioned about his gun control views at his Senate confirmation hearing.

House Minority Leader Kevin McCarthy, R-Calif., responds during his weekly news conference at the Capitol in Washington, March 18, 2021.

House Minority Leader Kevin McCarthy, a Republican, said Biden's moves would "trample over" the constitutional right to bear arms.

"He is soft on crime but infringes on the rights of law-abiding citizens. I won't stand for it. And neither will House Republicans. Follow the Constitution!" McCarthy tweeted.

The National Rifle Association, a major gun rights group, has said it will fight Biden's executive actions.

John Feinblatt, president of the nonprofit Everytown for Gun Safety, praised Biden's actions, particularly on ghost guns, saying that will "undoubtedly save countless lives."

"We are glad to hear the administration's commitment that today's actions are just the beginning and look forward to continuing to work closely with them to end gun violence in this country," Feinblatt said in a statement.