Dec. 28 (UPI) -- Former Vice President Joe Biden said Friday he would not comply with a Senate subpoena to testify in President Donald Trump's impeachment trial, but clarified on Twitter Saturday adding he would respond to a "legitimate congressional oversight request."
In comments to the Des Moines Register editorial board in Iowa, he said if Senate Republicans attempted to subpoena him in their attempt to defend the president, he would not comply.
"You guys are going to cover for three weeks anything that I said and [Trump's] going to get away," Biden said. "You guys buy into it all the time. Not a joke ... Think what it's about. It's all about what he does all the time, his entire career. Take the focus off. This guy violated the Constitution. He said it in the driveway of the White House. He acknowledged he asked for help."
Biden appeared to back away from that statement Saturday, saying on social media that such requests should go directly to witnesses with knowledge of the president's conduct.
"I want to clarify something I said yesterday. In my 40 years in public life, I have always complied with a lawful order and in my eight years as VP, my office - unlike Donald Trump and Mike Pence - cooperated with legitimate congressional oversight requests," Biden said.
"But I am just not going to pretend that there is any legal basis for Republican subpoenas for my testimony in the impeachment trial. That is the point I was making yesterday and I reiterate: this impeachment is about Trump's conduct, not mine," he added.
Earlier this year, Trump urged Ukrainian President Volodymyr Zelensky to start an investigation into Biden and his son Hunter Biden, who served on the board of a Ukrainian gas company from 2014 until this year, suggesting wrongdoing by the two.
Democrats claimed that Trump held up military aid to Ukraine until Zelensky complied to investigate Biden, who continued to be a frontrunner in the Democratic presidential primary. Trump's supporters said the president was only concerned about corruption and his call for the Bidens to be investigated was proper.
Senate Republicans have floated subpoenaing Biden to testify about his Ukraine role in Trump's impeachment trial.
"No one's taken as much heat and as many lies thrown at them as I have, but again, this is not about me," Biden said on the campaign trail Saturday. "It's not about my family. It's about the nation. And we have to reach out and unify this country."
Biden has called the Trump administration the most corrupt "in modern American history."
Senate Minority Leader Chuck Schumer, D-N.Y., has called for at least four witnesses to testify: acting White House chief of staff Mick Mulvaney, former national security adviser John Bolton, senior adviser to the acting White House chief of staff Robert Blair and Office of Management and Budget official Michael Duffey.
Several Trump administration officials refused to testify during the House hearings on impeachment,