By Jan Strupczewski and Renee Maltezou BRUSSELS/ATHENS (Reuters) - Talks on ending a deadlock between Greece and its international creditors broke up in failure on Sunday, with European leaders venting their frustration as Athens stumbled closer towards a debt default that threatens its future in the euro. European Union officials blamed the collapse on Athens, saying it had failed to offer anything new to secure the funding it needs to repay 1.6 billion euros (£1.15 billion) to the International Monetary Fund by the end of this month. Athens insists it will never give in to demands for more pension and wage cuts.