The International Monetary Fund said it could continue to support Ukraine with bailout funding even if Kiev does not reach a debt restructuring deal with private creditors.
The EU's Economic Affairs Commissioner Pierre Moscovici said he believed "more than ever" that a debt deal was possible between Greece and its creditors.
Greek Prime Minister Alexis Tsipras was expected to meet with Angela Merkel in Brussels after the EU's top official for the euro said a breakthrough bailout deal could be "days" away.
Greek Finance Minister Yanis Varoufakis warned that EU leaders had a duty to avoid a historic "failure" and urged a swift accord in Greece's debt talks with its creditors.
OPEC's announcement that it is keeping crude output levels unchanged again, despite a collapse in oil prices, reflects the growing influence of booming US shale.
OPEC ministers gather for an eagerly awaited meeting which is widely expected to leave its output levels unchanged, despite the recent oil price collapse and global oversupply.
European Commission head Jean-Claude Juncker said that "challenging" negotiations with Greece would continue, after late-night talks with premier Alexis Tsipras broke up without a deal.