Romania has started main construction work on the facility at Deveselu Air Base, which will host the controversial European land-based anti-missile defence (AMD) system.
Representing the second phase of the four-phase European Phased Adaptive Approach (EPAA) initiative, the facility is scheduled to become operational by the end of 2015.
Romania has signed a bilateral agreement with the US for construction of an Aegis ballistic missile defence system, including missile defence radar and standard missile-3 (SM-3) interceptors at Deveselu Air Base, in September 2011.
Speaking during the groundbreaking ceremony, Nato deputy secretary general, Alexander Vershbow, said the facility represents a vital link in the chain of assets provided by the alliance members, and will serve as an important part of Nato's overall missile defences in Europe.
''This facility will not threaten anyone, but bring better protection for the people, the forces and the territory of the allied countries in Europe,'' Vershbow said.
US Under Secretary of Defence for Policy James Miller was quoted by Agence France Presse, saying: ''What we are initiating here today is a powerful and tangible manifestation of our solemn commitment to mutual security in Europe.''
Involving deployment of Aegis-equipped warships in the Mediterranean, and the construction of an early warning radar station in Turkey, the first EPAA phase went operational in January 2012.
Scheduled for completion in 2018 and 2020 respectively, the third and fourth phases involve establishment of a missile-interceptor base with upgraded missiles and an improved command-and-control system in Poland, and deployment of advanced interceptor missiles to counter both intermediate-range missiles and intercontinental ballistic missiles (ICBMs) threats.
The Nato's AMD shield project seeks to counter threats from rouge states, such as Iran and North Korea, but has attracted opposition from Russia, due to fears that it could weaken its strategic missile capability.
Image: Nato deputy secretary general Alexander Vershbow and other military officials during the ballistic missile defence groundbreaking ceremony in Romania. Photo: courtesy of NATO.