WASHINGTON (AP) — A business associate of a key figure in the investigation into former Trump campaign chairman Paul Manafort has been charged with failing to register as a foreign agent, federal prosecutors in Washington said Friday.

W. Samuel Patten was expected to appear in court later in the day.

Patten was charged by way of a criminal information, a document that can only be filed with a defendant's consent and that typically signals a guilty plea is planned.

Patten was a business associate of Konstantin Kilimnik, a man U.S. authorities have said has ties to Russian intelligence.

Kilimnik worked closely with Manafort, who was found guilty this month of eight financial counts. Kilimnik also is a co-defendant in a pending case against Manafort in Washington that accuses them both of witness tampering.

Court papers don't refer to Kilimnik by name, but say Patten worked with a Russian national on lobbying and political consulting services.

Prosecutors say Patten's company was involved in lobbying work in the United States and the Ukraine, but that he failed to register as a foreign agent with the Justice Department as required by law.

The case was brought by the U.S. attorney's office in Washington and not by special counsel Robert Mueller, whose team has been investigating potential coordination between Moscow and the Trump campaign.

But Andrew Weissmann, one of the lead Mueller team attorneys in the Manafort prosecution, was seen at court Friday ahead of Patten's appearance.