Senate Judiciary Committee chair Lindsey Graham (R-SC) defended his investigation into 2020 candidate Joe Biden on Monday after Biden, with whom Graham has a decades-long friendship, slammed the senator for the probe.

During a radio interview with Fox News host Brian Kilmeade, Graham argued that his investigation, which is based on President Donald Trump’s debunked conspiracy theory that Biden ousted a Ukrainian prosecutor to protect his son, has “nothing to do with friendship.”

“When Joe Biden was vice presidential nominee in 2008, he tore the bark off John McCain and Sarah Palin,” the Republican lawmaker said. “Nobody asked him, ‘Hey well, that hurt your friendship.’ It didn’t hurt my relationship because that was the job he was assigned.”

Graham also addressed Biden’s assertion that Trump “is now essentially holding power over him that even the Ukrainians wouldn’t yield to.”

“Don’t worry about me. I’m fine, Joe,” the senator said.

Graham claimed that he was launching the investigation because “somebody needs to do it” despite his friendship with Biden and Sen. Chris Coons (D-DE).

“If they can’t withstand me doing my job, then it’s not the friendship I thought we had,” he said.