Former Vice President Joe Biden said President Donald Trump would be "abdicating the responsibility of the presidency" if he chose to avoid an interview with special counsel Robert Mueller's Russia probe by pleading the Fifth Amendment.
"That to me is constitutionally impermissible as an individual. It's an abhorrent notion as a sitting president of the United States of America," Biden said in an MSNBC interview that aired Thursday.
Biden's latest remarks come after an interview with CNN in which he said that if he were Trump's lawyer, he would probably advise the president not to speak to the special counsel. The president "has some difficulty with precision," Biden told the news network Tuesday.
Trump's legal team has reportedly mulled over the idea of compromising on a face-to-face interview with the special counsel. Some of the president's advisors have told reporters that White House lawyers are considering sending written submissions to some of the questions that might be presented to Trump.
Other people close to the president, including political strategist and Infowars regular Roger Stone, Newsmax publisher Chris Ruddy and former House Speaker Newt Gingrich, have also suggested Trump only offer written responses to investigators, according to Politico.
The Fifth Amendment to the Constitution grants Americans the right not to "be held to answer for a capital, or otherwise infamous crime, unless on a presentment or indictment of a Grand Jury, except in cases arising in the land or naval forces, or in the militia, when in actual service in time of War or public danger."
The White House has not said that the constitutional protection could be invoked, but some legal experts have said that pleading the Fifth may be Trump's only way of avoiding an interview with the special counsel.
The worry in the White House is that Trump — who has previously contradicted his administration on matters relating to Russia — could incriminate himself and be charged with lying to investigators, The New York Times reported last week.
"If the president took the Fifth, he is by definition, in my view, abdicating the responsibility of the presidency of the United States," Biden said.
CNBC has reached out to the White House for comment.
Biden, whose name is often included in a growing list of potential Democratic presidential nominees for the 2020 race, said he has "plenty of time" to decide whether or not to run for president.
As Mueller's investigation into the Trump campaign's ties to Russia sharpens its focus, Biden told MSNBC that the Trump administration has been "derelict in their duty" to respond to evident Russian election interference.
"What we do know is, their attempts are continuing," Biden said, referring to various reports — and recent statements from CIA director Mike Pompeo and Secretary of State Rex Tillerson — that Russia is attempting to influence the upcoming congressional midterm elections.