Sen. Tim Kaine (D-Va.) said Tuesday that the reported pending departure of Deputy Attorney General Rod Rosenstein would "raise the stakes" of next week's confirmation hearings for President Trump's nominee for attorney general, William Barr.

Kaine said on CNN's "New Day" that Rosenstein has allowed special counsel Robert Mueller's investigation into Russian interference in the 2016 election to "go forward," adding that he has "deep concern" about what Barr will do

"William Barr was sending freelance memos to the Trump administration making a case to undercut the Mueller investigation," Kaine said. "So the deep concern will be if he comes in and Rosenstein is gone, is this just a, you know, preface to either undercutting the investigation or trying to keep the results of it hidden from the American public."

Kaine was referring to a memo that Barr reportedly gave to the White House last June in which he said he was concerned that Mueller was probing possible obstruction of justice by Trump.

Barr said in the memo that Mueller's investigation is based on a "fatally misconceived" theory, The Wall Street Journal reported in December.

Trump has frequently lashed out during his presidency at the Department of Justice over the Mueller investigation, which Trump has described as a "witch hunt."

Former Attorney General Jeff Sessions drew the ire of Trump for recusing himself from overseeing that investigation, and Trump in November forced Sessions to resign.

Because Sessions recused himself, Rosenstein took the reins of overseeing the probe and ultimately appointed Mueller as the special counsel.

Kaine said Tuesday that he has a "real hard time" interpreting the news of Rosenstein's looming departure, adding that there are a range of questions he wants senators on the Judiciary Committee to ask Barr.

"Will he enable it to have the resources it needs? And he will make sure that the results are available to Congress and the American public? Those questions assume greater importance," he said.