Former Presidents George W. Bush and Obama are expected to deliver eulogies at Sen. John McCain's (R-Ariz.) eventual funeral, NBC News reported Saturday.

The news that the two former presidents plan to speak at the event comes amid revelations that those close to McCain have informed the White House that they plan to have Vice President Pence attend the senator's funeral - but not President Trump.

The New York Times reported earlier on Saturday that McCain's funeral is expected to take place at the Washington National Cathedral.

The 81-year-old McCain is currently undergoing treatment for an aggressive form of brain cancer that he was diagnosed with last year.

In an audio excerpt from his forthcoming memoir, "The Restless Wave: Good Times, Just Causes, Great Fights, and Other Appreciations," aired by NPR this week, McCain acknowledges that he doesn't "know how much longer I'll be here."

The senator has often had a contentious and rocky relationship with Trump. In excerpts from his upcoming memoir, McCain offers a sharp rebuke of the president, questioning his convictions as a leader and hitting him for his attacks on refugees and the press.

"I'm not sure what to make of President Trump's convictions," he writes.