WASHINGTON (AP) — The co-founder of a Washington opposition research firm that produced a dossier of salacious allegations involving President Donald Trump is to be interviewed by the Senate Judiciary Committee next week.

A person familiar with the discussions between Glenn Simpson and the committee says Simpson has agreed to cooperate with the panel and will appear for a closed-door interview on Aug. 22. The person says the interview will be transcribed.

The person spoke on condition of anonymity to discuss the private interactions of the committee. Simpson runs Fusion GPS, which hired the British intelligence officer who produced the dossier containing allegations of ties between Trump and Russia.

The Judiciary Committee is one of several probing Russia’s interference in the 2016 election and any possible collusion with Trump associates.