Qatar believes that secret meetings between Kushner and leaders from the U.A.E., its regional rival, may have led to Trump's endorsement of the U.A.E.'s naval blockade of Qatar. The country also believes that Kushner took an anti-Qatar stance after negotiations fell apart between his family business and Qatar investors.

But when the country's representatives visited Washington in January, they did not share their information with Mueller in order to preserve their country's relationship with the U.S., three sources told NBC.