ATHENS (Reuters) - Greek Prime Minister Alexis Tsipras on Monday called for 'a strong national front' to negotiate a way out of the country's debt crisis, after Greeks overwhelmingly rejected tough austerity terms set by international creditors. "We must move forward immediately with negotiations.. a strong national front must be created to seek an immediate solution," Tspiras told Greek President Prokopis Pavlopoulos after the vote. He is asking the president to convene a meeting of political party leaders. (Reporting By Michele Kambas)