Senior Gulf leaders were thought to be trying to negotiate a peaceful departure for Sheikh Khalid, but sources indicated he might have to be "made to leave one way or another" if he did not go quietly.
Sheikh Khalid was Crown Prince for much of the reign of his father, who came to power in 1948 and at his death at the age of 92 was the last remaining of the seven local rulers who founded the UAE in the early 1970s.
After he was deposed he went into exile and mounted a sometimes eccentric campaign to regain his position from New York and London.
He hired a British lawyer, Peter Cathcart, usually a family solicitor based in Uxbridge; a Californian public relations firm; and a Washington lobbyist to press his case.
Key to his argument was a claim that his brother was developing close relations with Iran, allowing his emirate to be used as a smuggling route.