BOSTON (Reuters) - Laws requiring background checks for buyers of guns and ammunition, as well as requirements that firearms be traceable, could sharply reduce gun deaths in the United States, according to a study published on Thursday.

A selection of handguns are seen for sale at the Pony Express Firearms shop in Parker, Colorado December 7, 2015. Many Americans are stocking up on weapons after the country's worst mass shooting in three years. Gun retailers are reporting surging sales, with customers saying they want to keep handguns and rifles at hand for self-defense in the event of another attack. REUTERS/Rick Wilking - RTX1XMR9

Many state-level gun regulations have little effect on the number of gun-related homicides and suicides. But “stand-your-ground” laws, which allow people to use deadly force in self-defense even if fleeing is an option, tend to raise the number of gun deaths, the study by Boston University researchers published in the Lancet medical journal found.

“Very few of the existing state-specific firearms laws are associated with reduced mortality, and this evidence underscores the importance of focusing on relevant and effective firearms legislation,” said Sandro Galea, dean of the School of Public Health at Boston University, an author of the study.

“Implementing universal background checks for the purchase of firearms or ammunition, and firearm identification nationally could substantially reduce mortality in the U.S.”

About 90 people die of gun-related injuries, both homicides and suicides, in the United States each day. The study found that nationwide adoption of background check laws as well as measures making it easier to track spent ammunition back to the gun that fired it could reduce gun-related deaths by as much as 80 percent.

The study looked at how deaths in 2010 were influenced by gun laws put into place in 25 states the year before.

It found that closing loopholes allowing gun buyers to avoid background checks when purchasing guns was the most effective way of reducing gun-related deaths.

Other regulations, including requiring more stringent record-keeping by gun dealers or mandating gun locks, had no measurable effect on gun-related deaths.

Opposition to gun regulations is strong in the Republican-led U.S. Congress, which has resisted measures pushed by Democratic President Barack Obama after a series of mass shootings including the massacre of 26 young children and educators in Newtown, Connecticut, in 2012.

In a January executive order, Obama imposed gun control measures that included requiring more gun buyers to undergo background checks.