US President Joe Biden said the conviction of a former police officer in the killing of George Floyd “can be a giant step forward in the march toward justice in America”.
But he warned: “We can’t stop here”.
White officer Derek Chauvin was filmed kneeling on African-American Mr Floyd’s neck for more than nine minutes, sparking mass protests against racism.
He was found guilty on Tuesday of second-degree murder, third-degree murder and manslaughter.
Sentencing is likely to happen in two months, and Chauvin could spend decades in jail. He is expected to appeal against the verdict.
In a phone call with Mr Floyd’s family after the verdict was announced, the president was heard saying: “At least now there is some justice.”
In televised remarks shortly afterwards, Mr Biden said that such a verdict was “much too rare”.
“We can’t leave this moment or look away thinking our work is done. We have to look at it as we did for those nine minutes and 29 seconds,” he said.
Vice-President Kamala Harris urged lawmakers to pass the George Floyd bill aimed at reforming policing in the US.
“This bill is part of George Floyd’s legacy. This work is long overdue,” she said.
People gathered outside the courtroom and on the intersection in Minneapolis where Mr Floyd was killed to celebrate the verdict.
Cheers broke out, drivers honked their car horns and people blocked traffic chanting: “George Floyd” and “All three counts”, referring to the three charges of which Chauvin was convicted.
“It’s a good day in Minneapolis,” said 21-year-old Kenneth Nwachi.
One local resident told the Associated Press news agency she felt grateful and relieved, while another said: “There’s some form of justice that’s coming.”
Crowds also gathered in other cities to celebrate the verdict.