Greek Prime Minister Alexis Tsipras has attacked the stance of "certain" creditors as "strange" because they rejected proposals presented by Athens to bridge a budget gap, a government official said on Wednesday.

Tsipras made the comments before heading to Brussels to meet the chiefs of Greece's three creditor institutions - the European Commission, the European Central Bank and the International Monetary Fund, the official said in a statement.

It did not say which proposals Tsipras was referring to, and which of the three institutions he was blaming for the deadlock.

"The non-acceptance of offsetting measures has never happened before. Neither in Ireland nor in Portugal. Nowhere!" the official quoted Tsipras as saying. "This strange attitude can only mean one of two things: either they do not want an agreement or they are serving specific interests in Greece."