Bill Clinton has issued a half-hearted apology for his lengthy, heated exchange with Black Lives Matter activists.

He was campaigning for his wife Hillary in Philadelphia when he was interrupted by activists holding signs and shouting “black youth are not ‘super predators’”, referring to a phrase Mrs Clinton used in 1996 to support her husband’s 1994 crime bill.

Mr Clinton responded to the activists: “I don't know how you would characterize the gang leaders who got 13-year-old kids hopped up on crack and sent them out into the street to murder other African-American children. Maybe you thought they were good citizens, she didn't. She didn't. You are defending the people who kill the lives you say matter.”

He also added that then-Senator Joe Biden had advised him to add provisions that would give offenders harsher prison sentences in order to gain Republican support.

On Friday, however, Mr Clinton adopted a more conciliatory approach and told an audience of more than 1,000 people in Erie, Pennsylvania, that maybe it was “a sign of old age” but it “bothered him” when protesters drowned him out, as reported by MSNBC.

“So I did something yesterday in Philadelphia. I almost want to apologise for it, but I want to use it as an example of the danger threatening our country,” he said.

“I rather vigorously defended my wife, as I am wont to do, and I realised, finally, I was talking past [the protester] the way she was talking past me. We gotta stop that in this country. We gotta listen to each other again,” the former president said.

Mr Clinton told the crowd that he went to the National Association for the Advancement of Colored People to call for change to his controversial 1994 crime bill.

“[It] led to some people going to jail for too long, in ways that cannot be justified,” he said.