Greece needs 50 billion euros over the next three years, including 36 billion euros more from EU lenders, to stabilize its finances even under existing creditor plans.
Greek Prime Minister Alexis Tsipras vowed to press ahead with a controversial bailout referendum as European leaders ruled out any fresh debt offer before Sunday's vote.
Ukrainian President Petro Poroshenko proposed constitutional changes giving sweeping powers to the regions but critically failing to address demands of pro-Russian militants in the separatist east.
NATO has vowed to hold "continuous" military exercises in eastern Europe to deter Russia but has yet to respond to a request by Baltic states for a permanent brigade.
Ukraine announced the immediate suspension of all Russian gas purchases after EU-mediated negotiations aimed at keeping supplies running for at least three more months broke down.
Nobody in the halls of the International Monetary Fund in Washington has any illusion: Greece is going to default, delivering a new blow to the global crisis bank's credibility.
Irish Prime Minister Enda Kenny said that Greece can still return to negotiations with its international creditors to avert a default and possible exit from the euro.
Russian Foreign Minister Sergei Lavrov expressed the hope that Brussels would avoid "negative scenarios" over Greece amid fears that the country is heading for a eurozone exit.
It has already been dubbed "Black Monday" -- jittery housewives, shoppers and business owners queued in vain at cash machines in Athens, where the country awoke to capital controls and shuttered banks.
The president of the European Commission will make his latest proposals later to try to avoid a Greek default, adding that Athens was 'centimetres' away from a deal when discussions broke down.
EU foreign policy chief Federica Mogherini said all sides had shown the political will needed to strike a nuclear deal with Iran, praising the "good results" despite a day of tough talks.