Former Vice President Joe Biden Joe BidenBiden on Trump's refusal to commit to peaceful transfer of power: 'What country are we in?' Democratic groups using Bloomberg money to launch M in Spanish language ads in Florida Harris faces pivotal moment with Supreme Court battle MORE said Tuesday that Congress should move forward with impeachment proceedings if the White House and Republicans work to block Democratic efforts to investigate matters "left undone" by special counsel Robert Mueller Robert (Bob) MuellerCNN's Toobin warns McCabe is in 'perilous condition' with emboldened Trump CNN anchor rips Trump over Stone while evoking Clinton-Lynch tarmac meeting The Hill's 12:30 Report: New Hampshire fallout MORE's investigation.

In an interview with ABC's "Good Morning America," the 2020 presidential candidate said that Democrats would have "no alternative" but to impeach President Trump Donald John TrumpBiden on Trump's refusal to commit to peaceful transfer of power: 'What country are we in?' Romney: 'Unthinkable and unacceptable' to not commit to peaceful transition of power Two Louisville police officers shot amid Breonna Taylor grand jury protests MORE if he were to block a congressional investigation into whether he obstructed justice by firing former FBI Director James Comey James Brien ComeyDemocrats fear Russia interference could spoil bid to retake Senate Book: FBI sex crimes investigator helped trigger October 2016 public probe of Clinton emails Trump jabs at FBI director over testimony on Russia, antifa MORE and attempting to fire Mueller.

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"There are elements of the report ... about seven or eight things that are left undone, he was not within his purview to investigate, he thought," Biden said of Mueller. "The Congress is attempting to take that up."

"If in fact they block the investigation, they have no alternative but to go to the only other constitutional resort they have, [which] is impeachment," he added. "But my job, in the meantime, is to make sure he's not back as president of the United States."

Joe Biden tells @GMA Congress is investigating elements "left undone" by special counsel Mueller.



"If in fact they block the investigation, they have no alternative but to go to the only other constitutional resort they have, [which] is impeachment." https://t.co/YS6D0nsVmt pic.twitter.com/KUqWzPHZ7v — ABC News Politics (@ABCPolitics) April 30, 2019

Biden's call for Congress to begin impeachment proceedings if the White House blocks its investigation falls short of the position of his fellow 2020 primary contender Sen. Kamala Harris Kamala HarrisHarris faces pivotal moment with Supreme Court battle Nearly 40 Democratic senators call for climate change questions in debates Joe Biden has long forgotten North Carolina: Today's visit is too late MORE (D-Calif.), who said at a town hall last week that Congress should begin impeachment proceedings now.

"We have very good reason to believe that there is an investigation that has been conducted which has produced evidence that tells us that this president and his administration engaged in obstruction of justice. I believe Congress should take the steps toward impeachment," she told a CNN town hall in New Hampshire.