President Joe Biden has urged unity to address the “hate that remains a stain on the soul of America” after a deadly mass shooting at a supermarket in Buffalo, New York, while state officials pleaded for federal action to end the “uniquely American phenomenon” of mass shootings.

Addressing an annual law enforcement ceremony at the US Capitol on Sunday, Mr Biden said he and his wife, Jill, prayed for those who were shot “by a lone gunman, armed with weapons of war and hate-filled soul”, and their families.

Authorities say Payton Gendron, a white 18-year-old male, opened fire at the supermarket on Saturday, killing 10 people, including a retired Buffalo police officer, and wounding three others. Most of the victims were black.

Law enforcement officials said the gunman had researched the local demographics while looking for places with a high concentration of black people.

“We must all work together to address the hate that remains a stain on the soul of America,” Mr Biden said at the 41st annual National Peace Officers’ Memorial Service honouring fallen law enforcement officers.

“Our hearts are heavy once again, but the resolve must never, ever waver.”

The White House said the Bidens would travel to Buffalo on Tuesday to grieve with the community.

Mr Biden did not address the calls by New York officials — Governor Kathy Hochul and Buffalo Mayor Byron Brown — for strong federal action to end mass shootings.

The president also did not mention gun control efforts that have stalled in Washington.

Mr Brown expressed frustration that “thoughts and prayers” and pledges to act were offered after every mass shooting, only to be blocked by “some on one side of the aisle”.

“It seems like there are those that believe owning a gun is more precious than the sanctity of human life,” the mayor told NBC’s Meet the Press.

“So I think people all across this country have to rise up. They have to speak more loudly and more clearly that there must be gun control in this country. This is a uniquely American phenomenon. These mass shootings don’t happen in other countries across the world.”

House Speaker Nancy Pelosi said tighter gun measures were “a huge priority” for Democrats and the White House, but she bemoaned the 60-vote threshold needed in the 50-50 Senate that has made it difficult to advance such legislation.

– AAP