The European Union still hopes a peace deal for Ukraine, brokered in Minsk can work despite ongoing battles between pro-Russian rebels and government forces, the EU foreign policy chief said on 17 February.

When asked by reporters if the Minsk agreement that stipulated a ceasefire from Sunday was a failure, Federica Mogherini said the deal still stands and the EU will insist on its full implementation.

"As long as there is a signed deal to which the parts still refer as something that needs to implemented, I will not say that there is a failure," she said.

The Moscow-backed rebels say the ceasefire does not apply to the main battlefront at the town of Debaltseve and have continued an all-out assault on the Ukrainian garrison there. Both sides had been due to withdraw heavy guns on Tuesday, but Kiev says it cannot do so while the rebels continue to advance.

"We knew from the beginning that it was going to be difficult, fragile, probably not black and white," Mogherini said. "What we need today is to work and insist for the process to get to a positive outcome," she added.

During the visit to Portugal's capital, Mogherini held a meeting with the Portuguese Prime Minister, Passos Coelho and conducted a news conference with the country's Foreign Minister Rui Machete.