President Barack Obama’s plans to modernize the U.S. nuclear arsenal over the next 30 years could cost taxpayers nearly $1 trillion, according to a new study that suggests the project’s long-term price tag will far outpace available Pentagon estimates.

The study, by the Center for Strategic and Budgetary Assessments, a Washington D.C.-based think tank that works closely with the Pentagon, is the latest attempt by independent researchers to determine the actual costs of Obama's ambitious plans for updating the nuclear triad — the intercontinental ballistic missiles (ICBMs), submarines and aircraft capable of delivering nuclear warheads. The White House, which announced plans to replace the aging arsenal in 2013, has to date only released a $73 billion estimate that covers fiscal years 2016 to 2020 — years before the program's costs are projected to spike.

Researchers Todd Harrison and Evan Montgomery found in the study that the actual cost could total $963 billion between 2014 and 2043. “Ultimately, this report finds that the Pentagon will … require as much as $12 to 13 billion per year in additional funding to support nuclear maintenance and modernization during the 2020s, when spending on U.S. nuclear forces will peak,” Harrison and Montgomery wrote.

Their findings are consistent with a widely cited assessment of $1 trillion published last year by the Monterey Institute for International Studies. Previous cost projections for Obama’s nuclear overhaul have varied widely, largely due to methodological differences, but most analysts agree that the official projection inadequately represents the costs because it stops short of the program’s “bow wave” — or peak spending years — in the late 2020s.

Many lawmakers and anti-nuclear advocates say the modernization plans are not affordable under budget restrictions that extend until 2021, but Harrison and Montgomery note that there are few feasible options for shaving down these costs. Aside from removing an entire “leg” of the nuclear triad — some experts have suggested that ICBMs are lowest priority and could therefore be dropped — the other "plausible" reductions they were able to identify “would not provide much savings when those savings are needed most,” in the next five years.

And considering that their projections will only spike nuclear spending to five percent of total U.S. defense spending even during the modernization "bow wave," scaling back these costs is not likely to be a top priority for lawmakers. "This is still a hunt for small potatoes," Harrison said at a press conference introducing the report on Tuesday.

The more important, long-term questions about the U.S. nuclear weapons program are strategic. “The heart of the matter is political,” said Tariq Rauf, director of the Disarmament and Arms Control program at the Stockholm International Peace Research Institute. “Hard political decisions need to be made justifying the retention of the nuclear triad in its current configuration.”