American four-time Olympic champion Michael Johnson says current protests following the death of George Floyd have produced "the most momentum around this issue I've seen in my lifetime".
Floyd, an unarmed black man, died while being restrained by a white Minneapolis police officer on 25 May.
Protests have been held across the US.
"I'm hopeful that a year from now we are not looking back at this time and nothing has happened, I'm hopeful that change truly does come," Johnson said.
Speaking to BBC Radio 5 Live Breakfast, the 52-year-old added: "We've seen black men killed by police before, we've seen those police convicted and sent to prison, that's happened and it still didn't change anything.
"The difference this time is that you have so many people talking about this issue, the protests continue, the conversation is only about this issue, and the momentum continues to grow.
"This is not only black people who are sounding this alarm, everyone who understands and appreciates fairness is fed up and they are demanding change."
Floyd's death has caused outrage and sparked a wave of protests against racial discrimination and police treatment of African Americans in cities across the US and the world.
Derek Chauvin, the police officer who knelt on Floyd's neck, has been charged with second-degree murder. Three other officers present face counts of aiding and abetting murder.
"It's the most momentum around this decades-old issue that I've ever seen in my lifetime," said Johnson.
"From that perspective, I've found it hopeful and promising that this murder of George Floyd has highlighted an issue that has been with us in this country and something that we have been dealing with as a country for over 50 years now.
"That is the systemic and institutionalised racism that happens every single day in this country."
He added that he hopes Americans will use their vote to bring about change at the November elections.
"I'm hopeful that we can sustain this through the November elections when a lot of people who typically support this type of movement have not voted, and that's a problem," he said.
"I'm hopeful that they understand that the biggest hammer you can swing at this is going to the ballot box and voting."