A Republican donor-turned ambassador to the European Union was scheduled be questioned by lawmakers on Capitol Hill Tuesday as part of the impeachment inquiry into President Trump.

Tuesday, the House had planned to meet with Gordon Sondland, who said he spoke to the President moments before his call with Ukraine's leader. 

However, the State Department has directed Sondland to not appear. 

A White House summary of that July 25th phone call shows President Trump pushed Ukrainian President Volodymyr Zelensky to investigate Joe Biden and his son, Hunter.

Text messages released by House Democrats show Sondland and other U.S. diplomats discussing that call, military aide to Ukraine, and a White House visit for Zelensky.

As the impeachment inquiry moves forward, President Trump says he's not concerned about a second whistleblower.

"It's a scam by the Democrats to try to win an election that they're not going to win in 2020" said President Trump. 

Democrats are also considering extreme measures to protect the original whistleblower's identity such as interviewing the person behind a curtain and disguising his or her voice.