The testimony from Barrack that he pushed for Qatar's interests could undermine charges by federal prosecutors in Brooklyn that he acted as an agent of the United Arab Emirates - one of the countries that implemented the blockade - without informing the U.S. attorney general, as required by law.

Barrack, 75, is not charged with acting as a Saudi agent, but the country is close with the UAE. He has pleaded not guilty, and argues his interactions with Middle Eastern officials were part of his role running private equity firm Colony Capital, now known as DigitalBridge Group Inc.

On Thursday, his fourth day testifying in his own defense, Barrack said that during an October 2018 phone call with Trump -following Khashoggi's murder in Saudi Arabia's consulate in Turkey - he urged the then-president to use global outrage over the killing "as a lever over this idiotic blockade."

U.S. intelligence says the murder of Khashoggi, a Saudi insider-turned-critic, was approved by Crown Prince Mohammed bin Salman, the de facto ruler. The prince has denied ordering the killing but acknowledged it took place "under my watch."

The blockade of Qatar by Saudi Arabia, the UAE and others began in 2017. Prosecutors say that during the blockade, Barrack told Rashid Al Malik - an associate also accused of being an Emirati agent - that the United States was considering hosting a summit to resolve the conflict. Al Malik, who is at large, then told UAE officials about the possible meeting, prosecutors say.

Barrack said he spoke to Qatar's ambassador in the United States as well as its foreign minister in June 2017. That came after Trump tweeted his support for the blockade on the Gulf nation.

Barrack said he then persuaded Trump administration officials to speak with Qatari counterparts, and eventually spoke directly with Trump to encourage him to host a summit at the Camp David presidential retreat to resolve the dispute involving U.S. allies.

"I had told him again from the cheap seats ... he should send his teams and conclude this to force Abu Dhabi and Saudi Arabia to the table," Barrack said. He denied telling Al Malik about the plans for the summit.

CROSS-EXAMINATION

Barrack in 2019 said at a conference in Abu Dhabi that it was a "mistake" to criticize the kingdom over the killing. He later apologized for the comments.

On the stand on Thursday, he said he should have prefaced the comments by saying that the taking of a life anywhere is unacceptable, but that he "hesitated" at the conference because of a lack of free speech in the UAE.

Prosecutors are expected to ask Barrack more about the comments when they begin cross-examining him later on Thursday.

(Reporting by Luc Cohen in New York; editing by Jonathan Oatis)

By Luc Cohen