By Kirsty Needham SYDNEY (Reuters) -The United States is seeking to seize a superyacht suspected of belonging to a Russian oligarch that is docked in the Pacific island nation of Fiji, according to an application for a restraining order filed on Tuesday by Fiji’s public prosecutor. The luxury vessel the Amadea is widely believed to be owned by Russian oligarch Suleiman Kerimov, sanctioned by the United States and European Union. The vessel arrived in Fiji a week ago after leaving Mexico 18 days earlier and crossing the Pacific. Police are investigating. Authorities in various countries have se…