On the first charge, Olson, 63, admitted that when he was the ambassador to Pakistan he failed to disclose that he received an $18,000 first-class ticket to fly to London for a job interview with a Persian Gulf investment firm.

On the second charge, he acknowledged that he illicitly lobbied US officials on behalf of the Government of Qatar in 2017, violating a federal “cooling-off” law that prohibited him from doing so for a year after his retirement from the State Department.

He was not charged with wrongdoing related to the diamonds – valued around $60,000 by federal officials – that an emir of Dubai gifted to his the-then mother-in-law or his British-Pakistani girlfriend’s, who later became his wife, tuition.

But the Justice Department has argued in connection with his sentencing that the episodes show a pattern of unethical behaviour.

Under federal sentencing guidelines, Olson could receive up to six months in prison, though his attorneys have said he should not have to serve any time behind bars.