Former Vice President Joe Biden Joe BidenOmar fires back at Trump over rally remarks: 'This is my country' Trump mocks Biden appearance, mask use ahead of first debate Trump attacks Omar for criticizing US: 'How did you do where you came from?' MORE said that Democrats should be vigilant during the upcoming confirmation hearing for President Trump Donald John TrumpOmar fires back at Trump over rally remarks: 'This is my country' Pelosi: Trump hurrying to fill SCOTUS seat so he can repeal ObamaCare Trump mocks Biden appearance, mask use ahead of first debate MORE's nominee to join the Supreme Court.

"Stay in the room, demand answers and keep pointing out that they have not given the material that was expected to the committee," Biden, a former chairman of the Senate Judiciary Committee, told reporters Monday as he attended a Labor Day parade in Pittsburgh.

The Senate Judiciary Committee's hearing for Trump's Supreme Court pick, Brett Kavanaugh, is scheduled to start Tuesday and last for multiple days.

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Republicans have spoken positively about Kavanaugh, a judge on the U.S. Court of Appeals for the District of Columbia Circuit, while a number of Democrats have expressed opposition to his nomination.

Democrats have been frustrated by the fact that they have been unable to see documents from Kavanaugh's time working as a staff secretary for former President George W. Bush. Republicans have not requested documents from Kavanaugh's time as staff secretary and have only requested papers from when Kavanaugh worked as a White House lawyer.

Biden also discussed the passing of Sen. John McCain John Sidney McCainCindy McCain endorses Biden: He's only candidate 'who stands up for our values' Biden says Cindy McCain will endorse him Biden's six best bets in 2016 Trump states MORE (R-Ariz.).

He gave a eulogy to his former Senate colleague last week and on Sunday told reporters at the Pittsburgh parade that McCain "was like a brother to me."

"As long as you were honorable, as long as you were honest, as long as you didn't leave anybody behind, as long as you treated people with dignity, you could always get on with John, even if you strongly disagreed with him like I did in the war in Iraq," Biden said. "But if in fact, if you didn't have those basic American values, then he didn't have a lot of respect for you."