ATHENS (Reuters) - Greek Prime Minister Alexis Tsipras will submit his resignation to the country's president later Thursday to clear the way for early elections on Sept. 20, a government official said. Tspiras, elected in January, is expected to make a televised state address on Thursday evening. Tsipras effectively lost his parliamentary majority after a rebellion by hardliners in his Syriza party who oppose a bailout agreement struck with international lenders. (Reporting By Renee Maltezou, writing by Michele Kambas, editing by Deepa Babington)