WASHINGTON (Reuters) - The co-founder of the firm that commissioned a dossier on Donald Trump during the presidential campaign last year is on vacation and will not testify at a Senate Judiciary Committee hearing on the Russia probe next week, his lawyers said in a letter released on Friday.

Glenn Simpson of Fusion GPS is on vacation through July 31 and will be traveling abroad through Aug. 3, his attorneys said in the letter, adding that they were “profoundly disturbed” that the hearing had been expanded due to “partisan agendas” to include allegations of Russian meddling in the U.S. election and possible ties between the Trump campaign and Russia.

Donald Trump Jr. and President Donald Trump’s one-time campaign manager Paul Manafort were due to testify on the same day as Simpson. His attorneys asked that Simpson be excused from appearing, adding that allegations he had failed to register as a foreign agent were “nothing more than an effort to smear him.”