(Bloomberg) -- Upgrading America’s nuclear missile arsenal will likely take longer than expected because of the complexities of pulling 1970s-era ICBMs out of aging silos and testing and installing replacement missiles and technology to run the system for decades to come, according to a congressional audit.

The Air Force faces the complicated challenge of removing a total of about 400 Minuteman-III intercontinental ballistic missiles and their command-and-control electronics at the rate of about 50 per year from silos and support buildings in various states of deterioration, some with water damage, the Government Accountability Office said in a report Thursday.

The difficulties -- which include extracting the missiles and nuclear payloads from the silos, repairing any structural decay, and installing customized electronics and the new weapon, all while maintaining other nuclear systems on alert -- mean the new ICBM won’t likely meet an initial 2029 deadline, the declassified GAO report warned.

“The Air Force is using multiple strategies to ensure on-time fielding, including financial incentives for the contractor to meet milestones,” of the Northrop Grumman Corp. program, according to the report. “Nevertheless, program schedule delays are likely” for reasons such as the complicated replacement process.

Modernizing the nation’s Cold War-era capacity to deliver nuclear weapons by air, land and sea -- the so-called nuclear triad -- remains a key Pentagon priority under the Biden administration after it was jumpstarted by President Barack Obama and continued by President Donald Trump. The effort is expected to cost as much as $1.2 trillion through 2046 for development, purchase and long-term support, the Congressional Budget Office estimated in 2018.

Read the full GAO report on the nuclear triad here

The GAO report is a primer on the risks inherent in the effort as U.S. officials say the nation faces a modernizing Russian nuclear arsenal and a burgeoning one from China, which in the “very near-term” will “possess a credible nuclear triad,” Admiral Charles Richard, the head of U.S. Strategic Command, told Congress last month.

Despite the urgency of the upgrades, “we found that every nuclear triad replacement program” -- including the B-21 bomber, new air-launched nuclear cruise missile, Columbia class submarine, “and every ongoing bomb and warhead modernization program -- faces the prospect of delays,” the report said.

Both the Pentagon and the Department of Energy “face challenges with sustaining existing nuclear triad systems,” GAO said.

Specifically, “the Navy and Air Force face difficulties in meeting some of STRATCOM’s operational requirements to be able to deploy additional quantities of systems above day-to-day requirements” and “some current triad systems have operational capability limitations that will only be mitigated once replacement systems are fielded.”

‘Aggressive’ Schedule

Northrop’s Ground Based Strategic Deterrent -- the land-based portion of the triad -- is at the heart of congressional debate over the Pentagon’s longer term spending plans. Thursday’s GAO report is likely to increase scrutiny, even among supporters, of Air Force plans to field the weapon.

Civilian Pentagon acquisition officials told GAO auditors the “schedule is aggressive and compressed compared to prior ICBM programs.”

Air Force documents acknowledge the step-by-step process needed to extract, upgrade and replace the missile system “introduces additional complexity to the schedule” as the service “will need to coordinate GBSD deployment activities with Minuteman III operations, depot maintenance, and sustainment activities to ensure that ICBM operations are not interrupted,” according to GAO.

The Air Force plans to put 57 launch facilities, including silos, annually through a programmed depot maintenance process in advance of GBSD fielding, with a plan to refurbish all over an 8-year period, said GAO.

Air Force documents indicate “it could take up to six months to complete the necessary restoration and conversion processes at each launch facility,” said the agency. “However, the Air Force has yet to evaluate all of the launch facilities and, accordingly, the full scope of work necessary to prepare the facilities” for use by a new missile “has yet to be determined.”

If the Air Force doesn’t resolve the issues with the launch facilities “in advance of the transition to GBSD, additional time could be needed for construction, which could result in delays to fielding.”

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