Spain's Economy Minister Luis de Guindos has criticised Greece's anti-austerity government for its "not very coherent" approach to negotiations over its finances and economy.
"We have wasted very precious time over the last three or four weeks," de Guindos said.
"They have not made a lot of friends."
Greece has relied on loans from European creditors and the International Monetary Fund since 2010.
It is in talks over the conditions for its next loan instalment, without which it could default as soon as next month.
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That has sent Greece's borrowing costs soaring.
De Guindos said he hopes significant progress in the negotiations will occur before a European finance ministers meeting on May 11.
"Time is running out," he said.
De Guindos spoke on the sidelines of the semi-annual meetings of the IMF and World Bank.
He criticised Greek officials for previously raising the spectre of default, only to then reverse themselves.
Greece's government needs to privatise state-owned companies, cut red tape and continue to reduce spending, he said.
"We are not discussing restructuring or forgiving the debt," he said.
"We are discussing the kind of reforms to make the Greek economy efficient, competitive and growing again."
