Former U.S. national security adviser John Bolton said Monday he would testify if subpoenaed during President Donald Trump¡¯s impeachment trial in the Senate, complicating Majority Leader Mitch McConnell¡¯s plan for swift proceedings with no witnesses.

¡°I have concluded that, if the Senate issues a subpoena for my testimony, I am prepared to testify,¡± Bolton said in a statement posted on his political action committee¡¯s website. Bolton didn¡¯t alert the White House ahead of time, according to a person familiar with the matter.

Bolton¡¯s pronouncement injects fresh drama into the trial, which has been delayed amid a stalemate over Democrats¡¯ demand that key administration figures ¡ª including Bolton ¡ª appear as witnesses. Senate Democratic leader Chuck Schumer said Bolton¡¯s statement increases pressure on Senate Republicans to back his call for additional testimony.