According to the spokesman, Athens must reach an agreement with its three major creditors — the European Commission, the European Central Bank (ECB) and the International Monetary Fund (IMF).
"The Greek government should do its best, and we hope that the remaining time will be used properly."
The announcement came ahead of an urgent Euro summit on the Greek bailout slated for Monday. The negotiators will make yet another attempt to reach a new agreement on Athens's debt relief before the expiry of its current bailout program on June 30.
Greece has been plunged into a deep economic crisis. Its overall state debt stands at $350 billion, of which $270 billion is owed to its three key lenders.