(Reuters) - Greece's Prime Minister Alexis Tsipras must decide whether to call a snap poll or a referendum if talks with the government's international creditors fail, a deputy speaker of the Greek parliament said on Monday. Athens has stuck to demands that its creditors propose less harsh terms for a cash-for-reforms deal after talks collapsed over the weekend, bringing Athens one step closer to a default that could tip it out of the euro zone. The initiative is now with the prime minister," Alexis Mitropoulos, a lawmaker from Tsipras's Syriza party and a parliament deputy speaker told Greek Star TV on Monday.