The Aegis Ashore weapon system launched an SM-3 Block IB guided missile during a test from Kauai, Hawaii, on May 21, 2014. The Navy will commission its new missile defense base in southern Romania on Friday, one of two European land-based interceptor sites.

NAPLES, Italy — The Navy will commission its new missile defense base in southern Romania on Friday, one of two European land-based interceptor sites for a NATO missile shield vehemently opposed by Russia.

The base represents a rare expansion of the U.S. footprint in Europe, and the even rarer construction of a new Navy base from the ground up.

The base in Deveselu will be the first to feature the Aegis Ashore ballistic missile defense system, a land-based version of the sophisticated radar tracking system installed on U.S. warships since 2004. Scheduled to become operational by the end of next year, the base — which is housed within a larger Romanian military installation — will be staffed by several hundred U.S. military, civilian and contract employees. A second site, in Poland, is scheduled to become operational by 2018.

Capt. William Garren will become the site’s first commander on Friday, officials said.

The site is part of a NATO missile defense shield pursued by two U.S. administrations as a defense against short- and intermediate-range ballistic missiles from Iran and other rogue states. But Russia has long criticized the project, claiming it was aimed against its own ballistic missile arsenal. The dispute has taken on new significance with recent fighting between Ukraine and separatists near the Russian border and the sharp deterioration of relations between the West and Moscow.

First announced by the George W. Bush administration in 2007, plans for an extensive missile shield focused on long-range interceptor sites, were cut back by the Obama administration in favor of an emphasis on short- and medium-range missiles.

The current “phased, adaptive approach” for missile defense in Europe will be based on ship-borne interceptors until the permanent land sites in Romania and Poland become fully operational. It calls for regular upgrades to interceptor technology and relies on an improving network of land- and space-based sensors.

U.S. warships equipped with Aegis systems began making regular patrols in the Mediterranean in 2011, and the U.S. is moving four of the destroyers to Rota, Spain, for the missions. An advanced radar system in Turkey was completed in 2012.

The site at Deveselu, part of the second phase, will host an Aegis SPY-1 radar and hold 24 Standard Missile-3 interceptors of the Block IB variant. A four-story radar deckhouse, similar to those used on a warship, will be moved to the site from the U.S. East Coast as part of construction.

The third and fourth phases were to focus on medium- and longer-range missile threats, with construction of the second land-based site in Poland and development of two new SM-3 variants. Defense Secretary Chuck Hagel canceled the fourth phase last year, which called for development of the long-range SM-3 variant by 2020.

The U.S. conducted the first test flight of its Aegis Ashore system on May 21 in Hawaii.

Naval Support Facility Deveselu officially entered the books last week with the start of the new fiscal year, according to Capt. Eric Gardner, officer in charge of the project in Naples. A small Friday ceremony will formally mark the turnover, he said. Construction at the site continues under a $134 million contract awarded by the military last year.

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