Thirty of the U.S. Air Force's fleet of more than 70 B-52 bombers have been converted to conventional-bombing capability only.

The work to eliminate the aircraft's capability to deliver nuclear weapons was conducted this summer at Barksdale Air Force Base in Louisiana to meet U.S. requirements under the New Strategic Arms Reduction Treaty with Russia -- known as the New START accord -- which came into effect in 2011.

The Air Force Global Strike Command said it will also convert 12 non-operational B-52H aircraft -- kept in storage by the service's 309th Aerospace Maintenance and Regeneration Group in Tucson, Ariz. -- to the conventional weapons-only variant.

All conversions were expected to be completed by early 2017, it said.

Under the New START accord, the United States and Russia are required to have no more than 1,550 deployed warheads; 800 deployed and non-deployed intercontinental ballistic missile launchers, submarine-launched ballistic missile launchers and nuclear-capable heavy bombers; and 700 deployed ICBMs, SLBMs and nuclear-capable heavy bombers.

U.S. efforts to transition 50 Minuteman III launch facilities across the command to an operational non-deployed status began last May, Air Force Global Strike Command said.

The B-52 Stratofortress is a long-range strategic bomber that first came into service in 1955. It was used in the Vietnam War and is undergoing modifications to remain an essential element of U.S. deterrence.