Barack Obama has paid tribute to the civil rights leader Joseph Lowery, calling the charismatic preacher “a giant who changed the face of America”.

Lowery died on Friday at the age of 98, his family said, after a lifelong fight against racial discrimination that saw him stand alongside Rev Martin Luther King Jr and other prominent civil rights figures throughout the 1960s.

“He carried the baton longer and surer than almost anybody,” Obama said in a statement posted to Twitter. “It falls to the rest of us now to pick it up and never stop moving forward until we finish what he started – that journey to justice.”

Lowery, who led the Southern Christian Leadership Conference (SCLC) he founded with King for two decades, was a staunch supporter of the former US president, describing Obama’s 2008 election victory as a turning point for the nation.

“America tonight is in the process of being born again,” Lowery said at an election-night celebration in Atlanta. He later gave the benediction at Obama’s inauguration.

In 2009 Obama awarded Lowery the presidential medal of freedom, the highest civilian honor in the US, in recognition of long service in the battle for racial equality.

“He did so much to carry us ever closer to the just, fair, inclusive and generous America promised in our founding ideals,” Obama wrote on Saturday. “With boundless generosity, patience, and moral courage, he mentored and encouraged a whole new generation of activists and leaders.

“Rev Joseph Lowery was a giant who let so many of us stand on his shoulders.”

In May 1970, United Auto Workers president Leonard Woodcock, in glasses and dark suit, locks arms with Coretta Scott King and Joseph E Lowery as they lead a protest march in Atlanta. Photograph: Anonymous/AP

A fiery preacher, Lowery’s long tenure as leader of the SCLC saw the organization return to financial stability and pressure American businesses not to trade with South Africa during the apartheid era.

But it was the election of the first African American president in 2008, 11 years after his retirement, that Lowery considered one of the greatest achievements of the civil rights movement.

In another high-profile moment, Lowery drew a standing ovation at the 2006 funeral of King’s widow, Coretta Scott King, when he criticized the war in Iraq, saying: “For war, billions more, but no more for the poor.”

The comment drew head shakes from then-president George Bush and his father, former president George HW Bush, who were seated behind the pulpit.

Lowery’s involvement in civil rights grew out of his Christian faith. He often preached that racial discrimination in housing, employment and healthcare was at odds with fundamental Christian values such as human worth and the brotherhood of man.

“I’ve never felt your ministry should be totally devoted to making a heavenly home,” he once said. “I thought it should also be devoted to making your home here heavenly.”

His wife, Evelyn Gibson Lowery, who worked alongside her husband of nearly 70 years and was head of SCLC/Women, died in 2013.