Democrats signaled their willingness to let some witnesses requested by Republicans testify as the House starts public impeachment hearings of Donald Trump this week, but only those people with knowledge of the president's actions. And not Hunter Biden or the whistleblower.

Ahead of the first session on Wednesday, Republicans gave the committee a list of witnesses they want called — including former Vice President Joe Biden's son, Hunter, and the anonymous whistle-blower whose complaint sparked the inquiry.

Democratic Reps. Jackie Speier of California and Sean Patrick Maloney of New York, both members of the House Intelligence Committee, said on Sunday morning political shows that there are Republican witnesses panel Chairman Adam Schiff could call — not Biden's son or the whistleblower, whose account has been corroborated by other witnesses.