Greece's Prime Minister Alexis Tsipras had at one stage warned foreign creditors that Athens would not repay 750 million euros (546.33 million pounds) due to the IMF in May unless they provided it with immediate liquidity, the Kathimerini newspaper reported on Saturday. Athens ultimately made the May 12 payment by emptying an International Monetary Fund holding account. Citing European sources, the newspaper said Tsipras made the threat in a May 8 letter to EU Commission President Jean-Claude Juncker, IMF head Christine Lagarde and ECB President Mario Draghi. The Greek government did not immediately respond to a request for comment.