Republican Senator Bob Corker (Tenn.) stepped up his public feud with Donald Trump on Friday, ripping the erratic president over his relationship with Secretary of State Rex Tillerson and denouncing his moves to “publicly castrate” his chief diplomat.

In an interview with The Washington Post, Corker, the Senate Foreign Relations chairman, said that Trump had undercut Secretary of State Rex Tillerson’s efforts to enlist China in reining in North Korea’s nuclear program by denigrating the diplomat.

“You cannot publicly castrate your own secretary of state” without limiting the options for dealing with North Korea, Corker told the Post. “It’s very irresponsible,” he added.

Two weeks ago, Tillerson told a news conference in Beijing that the United States was directly communicating with North Korea on its nuclear and missile programs.

The next day, however, he was publicly humiliated by Trump who tweeted that Tillerson was “wasting his time” trying to negotiate with North Korean leader Kim Jong Un.

“The greatest diplomatic activities we have are with China, and the most important, and they have come a long, long way,” Corker said.

“When you jack the legs out from under your chief diplomat, you cause all that to fall apart,” Corker told the Post, adding that working with China was the key to reaching a peaceful settlement with North Korea.

“When you publicly castrate your secretary of state, you take that off the table.”

Corker’s remarks come after a war of words with Trump in the last week.

Last Sunday, Trump took to Twitter to attack Corker, accusing him of not having “the guts to run” for reelection and claiming Corker “begged” him for an endorsement.

Corker fired back, calling Trump’s White House “an adult day care center.”

The Republican senator, who announced last month he wouldn’t seek reelection in 2018, later told The New York Times that Trump could put the U.S. “on the path to World War III.”

“He concerns me,” Corker said. “He would have to concern anyone who cares about our nation.” ShareTweet