(Reuters) - Democratic presidential contender Pete Buttigieg said on Thursday that when he used the phrase “all lives matter” in a 2015 speech he did not understand it had been adopted by critics to devalue the Black Lives Matter movement.

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Buttigieg, the mayor of South Bend, Indiana, and fast-rising 2020 White House candidate, told reporters he had not used the phrase again once he became aware it was sometimes used to undermine the Black Lives Matter movement to fight police violence and racism against African-Americans.

“At that time, I was talking about a lot of issues around racial reconciliation in our community. What I did not understand at that time was that phrase ... was coming to be viewed as a sort of counter slogan to Black Lives Matter,” Buttigieg told reporters after appearing before a conference of black activists in New York.

“Since learning about how that phrase was being used to push back on that activism, I’ve stopped using it in that context,” he said.

Buttigieg, who reported earlier this week that he raised $7 million for his presidential bid during the first quarter of this year, used the phrase in a 2015 State of the City speech in South Bend, where he has been mayor since 2012.

During the speech, he talked about the need to respect the risks taken by police officers and also recognize the need to overcome the biases implicit in the justice system.

“We need to take both those things seriously, for the simple and profound reason that all lives matter,” he said in 2015, according to a transcript published by the South Bend Voice.

Democratic presidential nominee Hillary Clinton was criticized later in 2015 for using the phrase “all lives matter.”

Wayne Messam, the mayor of Miramar, Florida, who last week declared his own bid for the Democratic presidential nomination in 2020, criticized Buttigieg on Thursday for his use of the “all lives matter” phrase.

“‘Black lives matter’ doesn’t mean that all lives do not matter, rather it is a cry for equal treatment in the greater circle of justice for all Americans,” said Messam, who is African-American.