Dutch finance minister Jeroen Dijsselbloem has poured cold water on optimism over a deal on Greece, saying it's "not theoretically possible this week".
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Greece must be "honest with voters", he added.
Earlier, Greek Prime Minister Alexis Tsipras sent the euro to a three-week high , saying he had submitted a "realistic plan" for economic reform to Greece's creditors.
However, those gains were reversed after Dijsselbloem's comments.
Greece urgently needs to reach an agreement over austerity measures with its creditors in order to unlock the €7.2bn bailout money it needs to make a €300m payment to the International Monetary Fund (IMF) on Friday. By Dijsselbloem's reckoning, though, it's game over.
Last night the leaders of Germany, France, the European Central Bank and the European Commission held emergency talks on the subject. Greek officials, however, were shut out of the talks.
Today Tsipras released a statement saying Greece had "not received an agreement plan from the [creditor] institutions, nor has there been contact between prime minister or some other official of a government with corresponding officials from the institutions".
Although Greece's proposals have not been unveiled, reports suggest it has agreed to overhaul its social security system and cut back pension reform, although it is thought it is still adamant its primary budget surplus - which has proved a sticking point in the negotiations - should be less than one per cent.