VIENNA (AP) — Acting at Ukraine’s request, the United States and 14 other nations on Tuesday formed a military observer mission intended to monitor the tense Crimea region, and a U.S. official said the team planned to leave within 24 hours.

Daniel Baer, the chief U.S. delegate to the Organization for Security and Cooperation, told The Associated Press that each country was contributing two individuals. But with more OSCE member nations expected to join, he said the mission could grow beyond its present strength of 30 people.