Khaled Meshal, who lives in Syria, called a two-state solution unacceptable because Hamas cannot envision living with Israel in peace and security.
Meshal spoke Saturday at a news conference, following a gathering of several Palestinian factional leaders in exile, reported KUNA, the Kuwait news agency.
Hamas envisions a Palestinian state based on the pre-1967 border with Israel, with Jerusalem as the capital, all Jewish settlements dismantled and full sovereignty over land, air and water, Meshal said.
In 1967, Israel invaded and occupied the West Bank and Gaza. In 2005, Israeli forces withdrew from Gaza but continued to control it through blockades and checkpoints.
Last December, Israel, in response to repeated rocket attacks, launched a major incursion into Gaza killing, by Hamas estimates, more than 1,300 Palestinian civilians, a third of them children, KUNA reported.