The United States sees Europe as its indispensable partner in addressing threats and challenges as well as opportunities, U.S. Defense Secretary Chuck Hagel said here on Saturday. Speaking at the 50th Munich Security Conference, Hagel said, "It's clear to us and president (Barack) Obama that our future requires a new and enhanced partnership with friends and allies, especially here in Europe." "The foundation of our collective security relationship with Europe has always been cooperation against common threats." Hagel said. Hagel admitted that meeting new challenges and choices will not be easy. "We must do so together." "U.S. will engage European allies to collaborate more closely, especially in helping build the capabilities of other global partners," Hagel continued. In face of budget constraints, Hagel said that the question is not just "how much we spend", but "how we spend together".