US President Joe Biden on Tuesday called the deadly mass shooting at a grocery store in Buffalo, New York, "domestic terrorism" and condemned white supremacy as a "poison running through our body politic".

"What happened here is simple and straightforward: Terrorism. Terrorism. Domestic terrorism," Biden told mourners in the upstate New York city where on Saturday a gunman killed 10 people and wounded three others in a rampage at a store in a predominantly black neighborhood. Of the 13 victims, 11 were black.

Payton Gendron, an 18-year-old white man who lived more than 200 miles away in Conklin, New York, has been charged in the massacre.

Biden called on Americans to reject the racist theory that authorities say appeared to have motivated the gunman to carry out the massacre.

"I call on all Americans to reject the lie, and I condemn those who spread the lie for power, political gain and for profit," Biden said.

Officials say Gendron allegedly wrote a 180-page document that included references to the racist and anti-Semitic "great replacement" conspiracy theory, which puts forward that a cabal of elites are engineering the replacement of whites with nonwhite immigrants.

"White supremacy is a poison," Biden told grieving families during an impassioned speech at a community center, "running through our body politic. And it's been allowed to fester and grow right in front of our eyes. No more, no more. We need to say as clearly and as forcefully as we can that the ideology of white supremacy has no place in America. None."

Biden condemned figures "who spread the lie for power, political gain and for profit", but he didn't name specific individuals.

The president and his wife Jill went to Buffalo to meet with leaders and residents of the city. They also went to the grocery store where the rampage took place before meeting with families of the victims and first responders.

Chiwuike Owunwanne, a community member who didn't meet with the president but was among the dozens of attendees present for his speech, said he was grateful for Biden's visit but underwhelmed by his remarks.

"To be honest, we've heard it before — many, many times before," he said of the speech. "At this point, you can basically copy-paste [the speech] because this has occurred in our communities throughout the country many times, dozens of times. I don't know whether a different speech can be given, but it feels like a different action is needed because whatever is being done clearly is not working."

For those outside the Delavan-Grider Community Center in Buffalo during Biden's speech there, some said they hoped the president would push for legislation specifically addressing anti-black hate crimes, similar to the bill he signed in 2021 after a wave of assaults against Asian Americans.

Asked about whether the Buffalo shooting could revive a push for gun safety legislation, Biden told reporters before boarding Air Force One to return to Washington that it would be "very difficult" to pass such measures. He added that he was "not going to give up trying".