Sen. Lindsey O. Graham (R-S.C.) said Thursday that the way President Trump responded to John McCain’s death was “disturbing,” and he acknowledged that he has been upset by some of the derogatory things Trump has said about the late senator.

“It bothers me greatly when the president says things about John McCain,” Graham said during an interview on “CBS This Morning.” “It pisses me off to no end, and I let the president know it.”

In recent months, Graham, who gave an emotional tribute to McCain on the Senate floor on Wednesday, sought to balance a friendship with the Republican senator from Arizona with his stated desire to work with Trump, a difficult task given the friction between the two men.

During the CBS interview, Graham criticized Trump for belatedly issuing a proclamation for U.S. flags to fly at half-staff until McCain’s burial this weekend. Flags were lowered at the White House on Saturday after McCain died but raised on Monday morning, complying with the minimum period prescribed by law.

Only after an outcry from veterans groups did Trump sign a proclamation directing that flags be lowered again for a period of time that has become tradition when sitting senators die.

“The way he’s handled the passing of John is just . . . was disturbing,” Graham told CBS host John Dickerson. “We finally got it right.”

Asked if he had called Trump after the White House flags were raised on Monday, Graham said: “No, but I called some people around him.”

The White House flag was back at half-staff Aug. 27, after it was raised to full-staff. It was lowered over the weekend following the death of Sen. John McCain. (Reuters)

Graham also said he would offer Trump some advice: Act more like McCain.

“You’ve got a lot of people you think are treating you unfairly. Fight back,” Graham said. “But you’re going to have to be a big man in a big office. McCain was a big man, worthy of a big country. Mr. President, you need to be the big man that the presidency requires.”

Even as McCain battled brain cancer, Trump continued to harshly criticize him for a vote against Republican health-care legislation. Trump also recently declined to mention McCain’s name at a signing ceremony for a defense bill named after him.

During the CBS interview, Graham said he plans to continue to work with Trump where he can.

“I am not going to give up on the idea of working with this president,” Graham said. “The best way I can honor John McCain is help my country.”