Democratic 2020 frontrunner Joe Biden said Congress will have "no alternative" but pursuing impeachment if President Donald Trump or his associates block investigations based on special counsel Robert Mueller's Russia report.

In an interview with ABC's "Good Morning America" broadcast Tuesday, Biden said that Mueller's 448-page report on Russian election interference included "about seven or eight things that are left undone."

"The Congress is attempting to take that up" for investigation as they should be doing, said Biden, who launched his presidential campaign last week. "And if in fact [Trump or his associates] block the investigation, they have no alternative but to go to the only other constitutional resort they have," which Biden said "is impeachment."

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Biden has taken aim squarely at Trump since announcing his candidacy, and now has established his own line in the sand on impeachment. But he said in the ABC interview that "my job in the meantime is to make sure he's not back as president of the United States of America."

The White House did not immediately provide a comment on Biden's remarks.

The findings of the special counsel's 22-month probe into Russia's meddling, potential collusion with the Trump campaign and possible obstruction of justice by Trump himself were finally revealed this month with the release of a redacted version of the report.

Mueller did not find sufficient evidence to show that Trump or people connected to him coordinated with the Kremlin. He made no determination on whether Trump obstructed justice, but noted 10 instances of potential obstruction by the president. Attorney General William Barr and Deputy Attorney General Rod Rosenstein concluded that an obstruction-of-justice charge was not warranted, based on the report.

Trump and Republicans have claimed that the outcome of the investigation offers a total exoneration of the president. Democrats, however, have seized on many of the details in the report, raising alarms about Trump's conduct and vowing to continue their own probes of Russian interference and other matters related to the president, including his finances.

Trump has made clear he intends to put up a fight. Last week, Trump and his business sued Democratic House Oversight Committee Chairman Elijah Cummings to block a subpoena seeking information from an accounting firm about Trump's finances. And Trump and his family filed a federal lawsuit Monday against Deutsche Bank and Capitol One to block more subpoenas from House Democrats.

The White House has refused to let some members of the administration comply with requests from House Democrats to testify. And Barr himself, scheduled to testify before House Democrats on Thursday, has reportedly threatened not to show up because of disputes with lawmakers over the format of the event. If he does skip the hearing, Democrats may subpoena him to testify.

The question of whether to pursue impeachment proceedings has split Democrats, including House Speaker Nancy Pelosi and several 2020 hopefuls. Presidential contenders Sen. Elizabeth Warren, D-Mass., and Sen. Kamala Harris, D-Calif., are among those who support impeachment.