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GENEVA, Aug 30 (Reuters) - Talks between U.S. and Russian officials this week are crucial for restoring a ceasefire in Syria, the United Nations Special Envoy Staffan de Mistura said in an appeal on Tuesday.

U.S. Secretary of State John Kerry and Russian Foreign Minister Sergei Lavrov failed in all-day talks in Geneva last Friday to reach a breakthrough deal on military cooperation and a nationwide cessation of hostilities, saying they still had issues to resolve.

Military officials from the two powers, who back opposite sides in Syria's five-year war, have been meeting for weeks and would continue talks to hammer out final details, they said at the time.

"Discussions between the Russian Federation and United States this week are crucial to efforts to restore the cessation of hostilities," de Mistura's spokeswoman Jessy Chahine told a news briefing in Geneva on Tuesday.

De Mistura also reiterated a call for a 48-hour humanitarian pause in the divided northern city of Aleppo to allow the safe delivery of supplies and medical evacuations.

The United Nations wants to deliver food and medicines to rebel-held eastern Aleppo and the government-controlled west. It also wants to repair the electricity system to deliver power and clean water supplies to 1.8 million people, amid fears of disease outbreaks.



(Reporting by Stephanie Nebehay, editing by Tom Miles and John Stonestreet) ((Stephanie.Nebehay@thomsonreuters.com; +41 22 733 3831; Reuters Messaging: stephanie.nebehay.thomsonreuters.com@reuters.net; twitter @StephNebehay))