In a declaration published on the website of his political action committee, former national security adviser John Bolton said that "if the Senate issues a subpoena for my testimony" in President Donald Trump’s impeachment trial, "I am prepared to testify."

Bolton, a key figure in the Ukraine scandal was not called to testify. On his statement he basically said that, should someone issue the subpoena, he would go and speak.

Bolton was the US National Security Advisor under the Trump administration from April 2018 to September 2019 ans made no mystery of his desire for regime change in Iran, Syria, Libya, Venezuela, Cuba, Yemen and North Korea. He had also repeatedly called for the termination of the Iran nuclear deal.