Lawyers for Payton Gendron, 19, moved to seek a plea agreement at a court hearing on Friday, less than two weeks after he pleaded guilty to state charges of murder and domestic terrorism.

An avowed white supremacist, he faces 27 federal hate crimes and firearms offences related to the racist massacre at a Tops Friendly Markets store.

Authorities said he targeted the supermarket because it was in a predominantly black neighbourhood of Buffalo, New York.

Gendron pleaded not guilty to the federal accusations in July. A conviction would make him eligible for the death penalty.

Gendron, who is from Conklin, New York, faces life in prison without parole on those counts.

"Just as Payton Gendron entered a plea of guilty to the indictment in county court, he is prepared to enter a plea of guilty in federal court in exchange of the same sentence, which is the sentence of life in prison, without parole," defence lawyer Sonya Zoghlin said, according to CNN.

Federal prosecutors were expected to discuss the issue with defence team early next year, the outlet reported.

The Justice Department has not decided what punishment it would seek.

Gendron, who was 18 at the time of the shooting, is set to be sentenced for state charges in February.

He was indicted on 10 counts of first-degree murder and 10 counts of second-degree murder, all of them as hate crimes, as well as three counts of attempted murder and a single count of illegal weapon possession.

Gendron additionally faced one count of domestic terrorism motivated by hate, becoming the first person charged under a newly enacted New York statute.

The gunman streamed live video of the May 14 assault to the social media platform Twitch after posting material online showing he had drawn inspiration from other racially motivated mass killings, authorities said.

Australian Associated Press