Sens. Chuck GrassleyChuck GrassleySenate panel subpoenas co-founder of firm tied to controversial Trump dossier Trump Jr., Manafort still haven’t agreed to testify before Senate panel Feinstein: Trump Jr. will be subpoenaed if he refuses to testify MORE (R-Iowa) and Dianne FeinsteinDianne FeinsteinSenate panel subpoenas co-founder of firm tied to controversial Trump dossier Feinstein: Trump Jr. will be subpoenaed if he refuses to testify The next battle in the fight against human trafficking MORE (D-Calif.) said the move came after Glenn Simpson, the co-founder of Fusion GPS, declined to speak before the committee on Wednesday.

Fusion GPS’ work on the Trump-Russia dossier, which contains memos compiled by former British intelligence agent Christopher Steele, was unrelated to the June 2016 Veselnitskaya/Trump Jr./Manafort meeting, The Washington Post reported, adding that work on the dossier was conducted on a different timeline.

Wednesday’s committee hearing is also scheduled to feature Donald Trump Jr. and President Donald Trump’s one-time campaign manager Paul Manafort. Browder, the son of Earl Browder, the former head of the CPU.S.A, is a London-based hedge-fund manager who is a vehement opponent of Putin’s Russia, and the main force behind the anti-Russia Magnitsky Act, which was the subject of the set-up meeting between Donald Trump Jr. and Russian lawyer Natalia Veselnitskaya, that is now the subject of Special Counsel Mueller’s investigation.

Fusion GPS was hired last June by a supporter of Hillary Clinton’s to investigate Trump’s dealings in Russian Federation. Instead, they will talk to the committee in a closed session.

Lawmakers have been clamoring to hear from Trump Jr. over his recently revealed meeting past year with a woman that represented herself as a Russian government lawyer offering damaging information on then-Democratic presidential nominee Hillary ClintonHillary Rodham ClintonHouse Intel panel to interview Kushner amid Russia probe Putin says he might be Russia’s president for life Senate panel subpoenas co-founder of firm tied to controversial Trump dossier MORE.

“Given the limitless scope of the hearing, as well as the privileges that Fusion GPS has already asserted, Mr. Simpson can not risk a waiver of those privileges at the hearing”. Browder has been a vocal critic of Fusion GPS’s credibility.

Last July, Browder filed a complaint with the Justice Department alleging that Simpson, Veselnitskaya, and others involved in the anti-Magnitsky effort, violated FARA, which requires individuals who work for foreign governments to provide details of their activities.

“We are profoundly disturbed that the scope of the proposed hearing has expanded, due to private and partisan agendas”, wrote Simpson’s lawyers, Joshua Levy and Robert Muse. They have also not confirmed they will testify.

The US Senate Judiciary Committee has issued a subpoena to compel Glenn Simpson, co-founder of a firm linked to the now infamous dossier on President Donald Trump, to testify at a hearing next week, according to Chairman Chuck Grassley and Ranking Member Diane Feinstein.

In addition, the attorney said that Simpson would “potentially” take the Fifth Amendment should he be subpoenaed to appear before the committee, he reported.