Rex Tillerson, who served a turbulent term as secretary of state under former US president Donald Trump, was called as a government witness Monday at the trial of a Trump ally accused of leaking intelligence to the United Arab Emirates (UAE).

Tillerson testified that he barely knew the defendant, Tom Barrack, once the chairman of Trump’s inaugural committee, or anything about his relationship with the UAE.

Instead, he spelled out how he would meet with Trump on a regular basis to discuss foreign policy, emphasizing that the sensitive conversations were supposed to stay confidential.

“You really don’t want outside parties to have access to that information and use it to their advantage,” Tillerson told a jury in New York.

Prosecutors have alleged Barrack provided inside information on how Trump administration officials viewed a UAE-led blockade of neighboring Qatar.

Tillerson testified he had advised Trump not to engage with the UAE on the issue, saying, “We needed to let them sort that out on their own.”

Tillerson also described one encounter with Barrack where he “called over to my office and expressed an interest in an ambassadorship”, he said. But Trump didn’t embrace the idea “so that was the end of it”, he said.

On cross-examination, Tillerson acknowledged having disagreements with Trump, but stayed clear of criticizing the former president.

He said they sometimes played “good cop-bad cop” in their public statements about adversaries such as North Korea.

The former Exxon Mobil chief executive is the highest-profile witness so far at the federal trial of Barrack, a billionaire private equity manager and Trump confidant who’s accused of secretly working as a foreign agent for the UAE.

Barrack, 75, has pleaded not guilty to that charge, along with obstruction of justice and false statements counts.

In 2018, Trump dumped Tillerson via Twitter, abruptly ending the service of a Cabinet secretary who had reportedly called the Republican president a “moron” but refused to step down, deepening disarray within the Trump administration.

Trump and Tillerson clashed on several foreign policy issues.

Barrack used “unique access” to Trump to manipulate him to advance the interests of the UAE, prosecutors claim, including helping to arrange a 2017 Oval Office meeting between Trump and Abu Dhabi’s Crown Prince Sheikh Mohammed bin Zayed Al Nahyan.

UAE officials allegedly were simultaneously consorting with Barrack, rewarding him by pouring millions of dollars into his business ventures.