Sen. Pat Roberts (R-KS) speaks with reporters ahead of the weekly policy luncheons on Capitol Hill in Washington, July 24, 2018.

Longtime Republican Sen. Pat Roberts of Kansas will not seek re-election in 2020, setting up an intense political scramble to replace him.

A person with knowledge of the 82-year-old senator's decision says Roberts will make the announcement Friday. The person declined to be named, saying Roberts wanted to make the announcement himself.

Roberts' office confirmed the news on Twitter on Friday.

@SenPatRoberts BREAKING: Senator Roberts will serve remainder of term and will not seek re-election in 2020.

Roberts has spent decades in Congress but faced pressure to step aside in part because he would have been 84 when facing voters. He also faced grueling primary and general election contests in 2014.

Roberts began his Capitol Hill career as an aide in 1967. He won a U.S. House seat representing western Kansas in 1980 and was elected to the Senate in 1996. But his longevity became a liability during his 2014 campaign.