TEL AVIV, Israel — An “issue” discovered during preflight checks pre-empted this month’s debut flight test of the new Arrow-3, a joint U.S.-Israel upper-tier missile interceptor already lagging nearly a year behind schedule.

Program officials refused to reveal the source of a problem potentially serious enough to warrant recalling the missile from its military launch site for corrective action at Israel Aerospace Industries (IAI), prime contractor for the joint U.S.-Israel program.

A Pentagon source said the maiden fly-out is now planned by the end of the year, “due to some additional work that is required to resolve the issue.”

U.S. Army Lt. Gen. Patrick O’Reilly, director of the Pentagon’s Missile Defense Agency, received a full program update last week in Berlin by Yair Ramati, his counterpart at Israel’s Ministry of Defense.

The two men were leading respective delegations at the annual Multinational Ballistic Missile Defense Conference and Exhibition, which the American Institute of Aeronautics and Astronautics held there Sept. 10-12.

A participant interviewed after the Berlin event credited Israel’s Ministry of Defense for its “prudent” decision to delay the flight, despite the “reasonably low risk” of test failure. “It probably could have flown successfully, but it’s always better to verify potential risks.”

He added that the additional downtime gained by the pre-empted flight would be used for validation ground testing to prevent current schedule slips from having a domino effect on initial deployment still planned for the end of 2015.

Developed by IAI with support from Boeing Co., its U.S.-based partner, the exoatmospheric, two-stage Arrow-3 uses pivoting optical sensors and its own upper-stage kick motor instead of separate control rockets to steer itself precisely into incoming targets.

It is designed to fly nearly twice as high at half the weight of Arrow-2, allowing multiple opportunities to shoot down advanced, maneuvering and possibly nuclear-equipped targets.

Plans call for integrating the upper-tier Arrow-3 and improved Block 5 versions of the operational Arrow-2 into a single national missile defense network. Pentagon budget justification documents presented to the U.S. Congress earlier this year estimated that the upper-tier Arrow-3 would provide a fourfold increase over the defensive battle space currently provided by the Arrow-2 system.

The improved Block 5 Arrow Weapon System network will include a new Long Range Detection Suite (LRDS) comprised of an unmanned airborne electro-optic sensor and a new ground-based S-band Silver Oak radar.

The developmental LRDS will eventually join Israel’s Green Pine and Super Green Pine radars, Citron Tree Battle Management Centers and Hazelnut Tree Launcher Control Center used in support of recently deployed Block 4 versions of the Arrow-2 based system.

New Block 4 versions of the Arrow system will participate in a joint air defense drill to begin here in October. Dubbed Austere Challenge, the monthlong drill is designed to hone interoperability between active defense units of the Israel Air Force and U.S. European Command.

More than 3,000 U.S. and Israeli troops are scheduled to participate in the upcoming event, which will include a U.S. Aegis ship, three land-based Patriot PAC-3 units, Israel’s Arrow, short-range Iron Dome and supporting elements for the developmental David’s Sling.