NEW YORK (Reuters) - The United Nations must deploy many more peacekeepers to Central African Republic to support government troops depleted by mass desertions during a recent surge in rebel attacks, the U.N. envoy to CAR said on Thursday. The CAR army, backed by U.N., Russian and Rwandan troops, has been battling armed groups that are seeking to overturn a Dec. 27 vote in which President Faustin-Archange Touadera was declared the winner. The country “is at serious risk of a security and peacebuilding setback,” envoy Mankeur Ndiaye said in an address to the Security Council. A substantial increase in the number of peacekeepers would give the mission greater mobility on the ground, Ndiaye said without saying how many more soldiers were needed. Seven peacekeepers have been killed since the rebels launched their offensive last month. The fighting has forced nearly 60,000 people to flee the country, compounding an already dire refugee crisis. Ndiaye said large numbers of CAR troops had deserted due to insufficient training and resources.