The war against terrorism and concerns over ballistic missile attacks are being linked to strains on U.S. Navy ships and resources, and growing concern that the service may be unable to meet operational needs.

Missions requiring Special Forces work or construction needs are stressing Navy resources, but of particular consideration, some defense analysts say, is the increasing need for ships to handle ballistic missile defense (BMD) operations.

“Our Seals, our Seabees, they’re under a lot of demand,” says Adm. Jonathan Greenert, chief of naval operations (CNO). “Ballistic missile ships are under demand.”

Speaking during a recent Pentagon briefing with reporters, Greenert said, “We track each and we got to keep an eye on it.”

The Navy’s BMD program is anchored by its fleet of destroyers and cruisers equipped with the Aegis combat system, and it is carried out jointly with the Missile Defense Agency (MDA). Under the Obama administration’s European Phased Adaptive Approach (EPAA) for European missile defense, BMD-capable Aegis ships have begun operating in European waters to defend the continent from potential ballistic missile attacks from countries such as Iran.

The U.S., Spain and NATO jointly acknowledged in October that as part of the EPAA, four BMD-capable Aegis ships are to be forward-homeported at Rota, Spain, in fiscal 2014 and 2015. BMD-capable Aegis ships also operate in the Western Pacific and Persian Gulf to provide regional defense against potential ballistic missile attacks from countries such as North Korea and Iran.

According to the Congressional Research Service (CRS), under MDA and Navy plans the number of BMD-capable Navy Aegis ships is scheduled to grow to 36 at the end of fiscal 2018 from 24 at the end of fiscal 2011.

“Some observers have been concerned that demands for BMD-capable Aegis ships are growing faster than the number of BMD-capable Aegis ships,” CRS reports.

The proposed 36 BMD-capable Aegis ships by fiscal 2018 would be seven fewer than projected under the fiscal 2012 budget. “Numbers of BMD-capable Aegis ships under the proposed fiscal 2013 budget compared to the fiscal 2012 budget might, other things held equal, reinforce such concerns,” CRS reports.

On the other hand, CRS says, A Defense Department official has been quoted as saying the EPAA mission to be performed by the four BMD-capable Aegis ships to be homeported at Rota would instead require 10 U.S.-homeported BMD-capable Aegis ships to perform.

On that basis, CRS says, it would appear that homeporting four BMD-capable Aegis ships at Rota could reduce demands for BMD-capable Aegis ships by six ships.

“In terms of the balance between demands for BMD-capable Aegis ships and available numbers . . . , the decline in the ramp-up rate in the number of BMD-capable Aegis ships under the proposed fiscal 2013 budget compared to the fiscal 2012 budget might be viewed as offset to a substantial degree, at least in certain years, by the plan to forward-homeport four BMD-capable Aegis ships at Rota,” CRS says.