By Chuck Ross

Former national security adviser John Bolton said Monday he is “prepared to testify” at the Senate impeachment trial for President Donald Trump if he is subpoenaed.

Bolton, who left the administration on Sept. 10, has previously said he would allow the federal courts to determine whether he has to testify to Congress about his White House tenure. Senate Democrats want Bolton to testify about his knowledge of Trump’s position toward Ukraine, while Republicans have said they want a speedy trial without witnesses.

House Democrats have caused a delay in the trial by withholding articles of impeachment as the Senate hammers out details about how the trial will be conducted.

“Since my testimony is once again at issue, I have had to resolve the serious competing issues as best I could, based on careful consideration and study. I have concluded that, if the Senate issues a subpoena for my testimony, I am prepared to testify,” Bolton said in a statement issued at a website for his political action committee.

House Democrats opted to vote on articles of impeachment before securing testimony from Bolton and other Trump administration officials, including acting White House Chief of Staff Mick Mulvaney.

Bolton and Mulvaney are likely to have information about Trump’s rationale in withholding the Ukraine aid. Democrats have asserted that Trump withheld the funding in order to pressure the Ukrainian government to open investigations into Joe and Hunter Biden.

Trump has denied a quid pro quo and said he withheld the money out of concerns with corruption in Ukraine and because European countries were not also providing security assistance.