Republican Sen. Chuck Grassley Charles (Chuck) Ernest GrassleyThe Hill's 12:30 Report: Ginsburg lies in repose Top GOP senators say Hunter Biden's work 'cast a shadow' over Obama Ukraine policy Read: Senate GOP's controversial Biden report MORE (Iowa) on Monday admonished President Trump Donald John TrumpBiden on Trump's refusal to commit to peaceful transfer of power: 'What country are we in?' Romney: 'Unthinkable and unacceptable' to not commit to peaceful transition of power Two Louisville police officers shot amid Breonna Taylor grand jury protests MORE for disparaging his White House chief of staff John Kelly John Francis KellyMORE for lacking crucial job skills.

“I wish President Trump would never discuss publicly any ill feelings has abt his CofStaff Gen Kelly. After all he was a Marine for 47 yrs. defended our freedoms. We need show respect,” Grassley tweeted.

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Grassley, the chairman of the Senate Judiciary Committee and second-most senior Republican in the Senate, made his comments after Trump said that Kelly lacked certain skills to manage the White House.

“He’s doing an excellent job in many ways. There are a couple of things where it’s just not his strength. It’s not his fault, it’s not his strength.” Trump said in an interview on “Fox News Sunday,” referring to Kelly.

“John, at some point, is going to want to move on. John will move on,” he said.

Senate Republicans generally have given Kelly high marks for his service as chief of staff. They saw him as an important disciplinary influence when he replaced Reince Priebus Reinhold (Reince) Richard PriebusLeaked audio shows Trump touted low Black voter turnout in 2016: report Meadows joins White House facing reelection challenges Trump names Mark Meadows as new chief of staff MORE last July.

Kelly, a former Marine Corps general, previously served as secretary of Homeland Security and head of the United States Southern Command.

Kelly faced criticism from Trump after he tried to save Homeland Security Secretary Kirstjen Nielsen Kirstjen Michele NielsenMore than million in DHS contracts awarded to firm of acting secretary's wife: report DHS IG won't investigate after watchdog said Wolf, Cuccinelli appointments violated law Appeals court sides with Trump over drawdown of immigrant protections MORE from being pushed out of the Cabinet.

Trump on Sunday said she needed to be tougher.

“I respect her a lot. She’s very smart,” Trump said on Fox. “I want her to get much tougher and we’ll see what happens there. But I want to be extremely tough.”