Gordon Sondland said that he had been recalled as the US ambassador to the European Union after his participation as a witness for the impeachment trial.
"I was advised today that the President intends to recall me effective immediately as United States Ambassador to the European Union," Sondland said in a statement.
Earlier on Friday another impeachment witness, Lt. Col. Vindman, was removed from the National Security Council, which some critics saw as retaliation on the part of President Donald Trump.
Sondland continued in his statement to thank the president for the opportunity to serve as an ambassador.
"I am grateful to President Trump to having given me the opportunity to serve, to Secretary Pompeo for his consistent support, and to the exceptional and dedicated professionals at the U.S. Mission to the European Union," he added.
Sondland testified about what he overheard in relation to a call by the president to the president of Ukraine, and whether a "quid pro quo" demand was made in exchange for an investigation into Joe Biden and his dealings in the country crippled by corruption.
Washington Post contributor and MSNBC analyst Eugene Washington responded to the firings by the Trump administration in a tweet calling it "outrageous and vile."
"This is how tin-pot dictators act. These are the stakes in November," he added.