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.