A court file showed on Saturday that federal prosecutors will summon former US Secretary of State Rex Tillerson to testify in the trial of Tom Barrack, the fundraiser for former President Donald Trump, on charges of illegally working as a foreign agent for the UAE.

Barak's defense disclosed the plans, in a letter to U.S. District Judge Brian Coogan, asking Tillerson to testify on Monday.

The defense said prosecutors confirmed they would contact Tillerson, but told the defense he would not be available after October 4 due to "personal matters."

Barak's lawyers said the State Department and Trump himself were aware of his contacts with officials in the Middle East, which indicates that Barak did not intend to be a foreign agent.

So far, the former foreign minister could not be reached for comment.

A spokesman for the attorney general's office in Brooklyn, where Barak is being tried, declined to comment.

Barak pleaded not guilty.

His lawyers said his contact with Emirati officials was part of his role in managing the private equity firm Colony Capital, now known as the Digital Bridge Group, and that there was no evidence that he had agreed to act on orders from Abu Dhabi.

Tillerson (the former CEO of ExxonMobil) held the State Department position for just over a year from 2017 to 2018 during the Trump presidency.

The jury selection trial began on 19 September.

During the first week, prosecutors provided emails and text messages from Barack and one of his colleagues that showed Emirati officials provided information about what (candidate) Trump had to say in a speech on energy policy in 2016.

Prosecutors said Barak never told the justice minister that he was working as an agent for the UAE, as required by federal law.

Michael Schachter (Barack's attorney) said in opening statements that there was no evidence that his client had agreed to work at the direction of the UAE.