The co-founder of a firm behind an unverified intelligence dossier about President Trump and his relationship with Russia will not testify before the Senate Judiciary Committee next week, after he was scheduled to do so, according to a Politico report Thursday.

On Wednesday, the committee had announced a July 19 hearing that included Glenn Simpson, the co-founder of the political and corporate intelligence firm Fusion GPS, as a witness.

This request raised the expectation that Simpson would provide details about the dossier, which was said to have been collected during last year's presidential campaign.

Most major media outlets only reported on the existence of the unsubstantiated dossier — leaving out specific details — after the chiefs of America's intelligence agencies in January presented then-President-elect Trump with a summary of the dossier.

BuzzFeed published the dossier in full.

The author of the dossier is Christopher Steele, a former British intelligence officer with MI-6, who once served in Moscow.

Steele was paid by Fusion GPS and later by Hillary Clinton supporters to compile the information as opposition research. The dossier, among other things, says that Russian officials tried to influence Trump by preparing to blackmail him with sex tapes and bribe him with business deals.

The request for Simpson to testify was voluntary and it's unclear if the committee will seek to subpoena him to appear. The committee is investigating Russia's election interference and whether the Trump campaign worked with Moscow.