“I’m not going to pretend that there are legal grounds for my testimony in the impeachment case on republican agendas,” Biden wrote on his Twitter.

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.

- Joe Biden (@JoeBiden) December 28, 2019

The former vice president clarified that this impeachment case concerns Trump, and not him.

Earlier it became known that Democrats in the US Congress could bring new charges to President Donald Trump as part of impeachment.