By Trevor Hunnicutt

WASHINGTON (Reuters) -The second deadly U.S. mass shooting in a week is putting new pressure on President Joe Biden to deliver on the gun control promises he made as a candidate.

A gunman on Monday killed 10 people, including a police officer, at a grocery store in Boulder, Colorado, just six days after another gunman fatally shot eight people at Atlanta-area day spas.

“I don’t need to wait another minute – let alone an hour – to take common sense steps that will save the lives in the future, and I urge my colleagues in the House and Senate to act,” Biden said at the White House on Tuesday.

The Democratic president called on the Senate to approve two bills passed by the House of Representatives on March 11 that would broaden background checks for gun buyers. In addition, Biden also called for a ban on assault-style weapons.

White House spokeswoman Jen Psaki told reporters Biden also is “considering a range” of executive actions to address gun violence. Such actions would not require congressional approval.

Biden, who took office in January, faces an uphill battle in winning congressional passage of gun-related measures he pledged during his presidential campaign.

The United States has the world’s highest rate of civilian gun ownership, RAND Corp research shows. There were more than 43,000 U.S. gun deaths last year, according to the Gun Violence Archive, in a country with a gun fatality rate consistently higher than other rich nations.

“I’ve beaten the National Rifle Association nationally twice, passed meaningful gun legislation at the federal level, and I’ll do it again,” Biden said last year at one of several campaign events focused on firearms violence, referring to the Republican-aligned NRA gun rights group.

“As president, I promise you I will get these weapons of war off the street again,” Biden added, referring to a national ban on assault-style weapons that lapsed in 2004.

CONGRESSIONAL ACTION

The numerous U.S. mass shootings have failed to prompt lawmakers to pass gun control legislation, thanks in large part to opposition from congressional Republicans and the NRA. The right to bear arms is enshrined in the U.S. Constitution’s Second Amendment and many Americans cherish gun rights.

Still, nearly 70% of Americans support adding “strong or moderate” federal gun restrictions, and ideas such as background checks and databases to track ownership have even greater public support, a 2019 Reuters poll found.

Biden’s fellow Democrats hold slim majorities in the House and Senate. Most bills require 60 votes in the 100-seat Senate to move forward, a tough hurdle for gun control legislation considering that Republicans hold 50 of those seats.

Democratic Senator Joe Manchin, a swing vote who holds near veto power over his party’s Senate agenda because of its razor-thin majority in the chamber, told reporters he does not support the House bills. Manchin and Republican Senator Pat Toomey instead favor their own bill, which would allow private sales of firearms without a background check.

Background checks are conducted to review a buyer’s criminal and mental health history and other factors that could bar someone from buying a gun.

A Senate panel held a hearing on gun issues on Tuesday.

“This is not and should not be a partisan issue,” Biden said. “It will save lives – American lives – and we have to act.”

Any new gun control measures signed by Biden would almost certainly face a legal challenge that could reach the Supreme Court, whose 6-3 conservative majority is seen as sympathetic to an expansive view of gun rights.

Biden has long embraced gun control. As a candidate, Biden pledged to hold gun makers accountable in the courts for firearms violence, to sign new laws restricting assault weapons and to expand background checks for gun sales.

As vice president under President Barack Obama, Biden was instrumental in seeking congressional approval of legislation after a 2012 mass shooting at a Connecticut elementary school.

After fierce NRA lobbying, Senate Republicans in 2013 thwarted legislation that would expand background checks, ban assault-style weapons and bar high-capacity gun magazines. The NRA since then has encountered internal upheaval and legal challenges.

Gun control activists have urged Biden to take executive action on matters they have said he can address unilaterally.

These activists have proposed that Biden direct the Justice Department’s Bureau of Alcohol, Tobacco, Firearms and Explosives to block the sale of self-assembled “ghost guns” without background checks or serial numbers to identify the finished product. They also urged Biden to name a permanent director of that bureau, which currently is led by an interim chief.

Gun control activists have been holding virtual meetings with senior White House aides Susan Rice and Cedric Richmond. These sessions have been focused on soliciting views rather than outlining policy action, according to people who attended, speaking on condition of anonymity.

(Reporting by Trevor Hunnicutt; Additional reporting by Lawrence Hurley, David Morgan, Jeff Mason, Susan Cornwell and Steve Holland in Washington, Nandita Bose on board Air Force One and Nathan Layne in Wilton, Connecticut; Editing by Heather Timmons and Will Dunham)