Top ranking Republican Senator Bob Corker (R-TN), the chairman of the Senate Foreign Relations Committee, expressed concerns Sunday that President Trump’s reckless threats toward other counties “could set the nation on the path to World War III.”

Trump spent the better part of the weekend on Twitter angrily condemning Corker, accusing him of being behind the P5+1 nuclear deal with Iran, and saying he’s not running for another term in office because “he doesn’t have the guts.”

Corker said that top administration officials are constantly trying to protect Trump from his own interests, and much of the work of today’s White House is “a situation of trying to contain him.”

Corker went on to say Trump’s irresponsible outbursts should be concerning to all Americans, and that he’s treating the presidency like it’s a reality television show. He also said Trump’s Twitter outbursts have in several instances harmed diplomatic efforts of Secretary of State Rex Tillerson.

While Trump has yet to respond to Corker’s latest comments, the last thing he’d said earlier in the day was that he expects Corker to “be a negative voice and stand in the way of our great agenda.”

Sen. Corker’s comments are an unprecedentedly public rebuke of Trump from his own party, but are seen as reflective of some other Republican leaders who are uncomfortable with Trump’s volatile behavior. It may also be a bigger problem than Trump expects if he’s totally alienated Corker, as the Republican majority in the Senate is small, and losing a top leader’s public loyalty could easily cost him some close votes.