ALEXANDRIA, Va. (AP) — A businessman who served as a key witness in special counsel Robert Mueller's investigation will remain in jail at least for now on charges he transported images of child pornography.

Lebanese-American businessman George Nader, 60, made an initial appearance Thursday in federal court in Alexandria. Prosecutors want him detained pending trial. Nader's lawyers say he's in poor health and should be released.

Nader's lawyers filed a motion seeking his conditional release, but it is filed under seal so its details are not public. After a bench conference of several minutes at Thursday's hearing, U.S. Magistrate Judge Ivan Davis ordered that Nader remain jailed, but expedited a detention hearing for Friday afternoon, where the issue can be discussed further. Davis also scheduled a preliminary hearing for Monday.

Nader was arrested earlier this week after flying to New York from the United Arab Emirates. At an earlier hearing in New York, Nader's lawyer, Christopher Clark, said his client came to the U.S. to receive treatment for heart disease.

Clark declined to comment after Thursday's hearing.

Nader's name shows up more than 100 times in Mueller's recently released report. It details his efforts to serve as liaison between a Russian banker close to Russian President Vladimir Putin and members of President Donald Trump's transition team.

Nader also served as an adviser to the United Arab Emirates, a close Saudi ally, and in April 2017 wired $2.5 million to a top Trump fundraiser, Elliott Broidy, through a company in Canada, The Associated Press reported last year. The goal was to persuade the U.S. to take a hard line against Qatar, a longtime American ally but now an adversary of the UAE.

The images depicting child pornography and bestiality were discovered on Nader's phone last year after they were confiscated under a search warrant apparently connected to the Mueller probe.

Nader pleaded guilty to an identical charge of transporting child-pornography images in Virginia in 1991. He was also convicted in the Czech Republic by Prague's Municipal Court of 10 cases of sexually abusing minors and sentenced to a one-year prison term in 2003.