In October 2006, tensions rose when Israeli Prime Minister Ehud Olmert invited a right-wing political party Yisrael Beiteinu, to join his coalition government. The party leader, Avigdor Lieberman, advocated an ethnicity based territory exchange, the Lieberman Plan, by transferring heavily populated Arab areas (mainly the Triangle), to Palestinian Authority control and annexing major Jewish Israeli settlement blocs in the West Bank close to the green line as part of a peace proposal. Arabs who would prefer to remain in Israel instead of becoming citizens of a Palestinian state would be able to move to Israel. All citizens of Israel, whether Jews or Arabs, would be required to pledge an oath of allegiance to retain citizenship. Those who refuse could remain in Israel as permanent residents.