House Democrats indicated on Wednesday (January 15) they would expand their case against Trump by including phone records and other documents provided over the weekend by Florida businessman Lev Parnas, who worked with Trump's personal attorney, Rudy Giuliani, to pressure Ukraine.
Schiff said material released on Tuesday showed Giuliani was acting at Trump's direction.
House Judiciary Committee Chairman Jerrold Nadler added: 'if the Senate doesn't permit the introduction of all relevant witnesses and all relevant documents that the House wants to introduce...then the Senate is engaging in an inconstitutional and disgusting cover-up.'
After weeks of delay, the House was poised on Wednesday afternoon to send the two impeachment charges - abuse of power and obstruction of Congress - passed on Dec.
18 against Trump to the Senate, clearing the way for a trial that will determine whether he is removed from office to start in earnest next week.
The trial in the Senate - controlled by Trump's fellow Republicans - is expected to end in his acquittal after several weeks of a televised proceedings, leaving him in office.
But it will focus attention on Trump's request that Ukraine investigate domestic political rival Joe Biden, just as the 2020 presidential campaign heats up.