August 30, 2018 9:21 AM EDT

South Carolina Sen. Lindsey Graham says President Donald Trump’s history of attacks on the late Arizona Sen. John McCain bother him “greatly.”

“It pisses me off to no end, and I let the president know it,” Graham, McCain’s longtime friend, said on CBS This Morning.

Trump and McCain had a long running feud that extended past the Arizona Republican’s death.

Trump in 2015 said McCain, who was a prisoner of war for more than five years during the Vietnam War, was “not a war hero.”

As the nation mourned McCain’s passing, Trump remained mostly silent, only recognizing the Senator’s “service to our country” and re-lowering the White House flag on Monday after flying it at full staff earlier in the day.

Graham, a Republican, said that while he’s still open to working with Trump, he’s bothered by the way the president has dealt McCain’s death.

“The way he’s handled the passing of John is just, was disturbing,” he said. “I am not going to give up on the idea of working with this president. The best way I can honor John McCain is help my country.”

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Write to Mahita Gajanan at mahita.gajanan@time.com.

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