The leaders of most Greek parties on Monday will issue a joint statement calling for a debt deal, Defence Minister Panos Kammenos, whose party is in coalition with the ruling Syriza party, said.

"There is no other option but a deal," Kammenos told reporters after a seven-hour meeting, adding: "Soon you will have the joint statement signed by all leaders except the Communist party ... giving strength to the prime minister to go to Brussels tomorrow and negotiate on behalf of the Greek people."