MINSK, Feb 12 (Reuters) - Talks between leaders of France, Germany, Russia and Ukraine on the Ukraine crisis in Minsk, Belarus, could continue for at least another five to six hours, a Ukrainian presidential aide said early on Thursday.

"We've got another 5-6 hours of work. At least. But we should not leave here without an agreement on an unconditional ceasefire. There's a battle of nerves underway," aide Valeriy Chaly said in a Facebook post.

Chaly made his comment after talks had already been underway for seven hours. (Reporting by Alessandra Prentice; Editing by Richard Balmforth)

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