Bill Taylor, the veteran State Department official who called freezing Ukrainian aid “crazy,” has been asked to give a deposition before House committees.

According to CNN, an interview has not yet been scheduled and will likely draw opposition from the White House and State Department, who have tried to block testimony from other players in the Ukrainian scandal.

Taylor became part of the story when Kurt Volker, former special envoy to the Ukraine, release a tranche of text messages between himself, Taylor and U.S. ambassador to the EU Gordon Sondland.

In the messages, Volker and Sondland particularly try to create a bridge between Rudy Giuliani and Ukrainian officials, eventually planning communications between President Donald Trump and Ukrainian President Volodymyr Zelensky centered on digging up dirt on the Bidens. Taylor is the only one who ever pushes back on the scheme, calling the freezing of Ukrainian military aid “crazy” and hinting that he may quit.

House Intelligence Committee Chair Adam Schiff (D-CA) expressed interest in talking to Taylor on Tuesday, calling him a “potentially important witness on the subject.”