President Trump’s ambitious plan to rebuild America’s overstretched military will likely add $683 billion to defense spending over the next decade, the Congressional Budget Office said in a report released Monday.

“If the new Administration’s goals for increasing the readiness, size, and capabilities of the military were pursued, cumulative costs would be $683 billion (or 12 percent) higher from 2018 through 2027 than costs of the Obama Administration’s final budget plan for those same years,” according to CBO’s projections.

Some of the increase is attributable to inflation and increases in existing programs, but about half of the difference, an estimated $342 billion, would come as a direct result of Trump's goals for expanding the size and capabilities of the U.S. military after 2018.

The CBO projection makes a number of key assumptions, including that mandatory spending limits imposed by Congress would have to be lifted.

The reports notes that defense funding for 2018-2021 remains subject to caps mandated by Budget Control Act of 2011, and that even if no new programs or initiatives were implemented during that time, just the cost of inflation would push the Pentagon’s budget to exceed the BCA caps by $295 billion.

Among the CBO’s assumptions:

  • The number of people serving in the armed forces would increase by about 237,000, or about 10 percent
  • The Navy would increase its fleet to 355 warships, nearly 30 percent higher than the current fleet
  • Purchases of new weapons would increase, as would spending for research on future weapons
  • Costs also would rise because growth in expenses for military personnel and for operation and maintenance that would continue to outpace inflation.

Trump’s fiscal 2018 budget request called for $574.5 billion in funding for the Defense Department, along with $65 billion for overseas contingency operations, mostly for the wars in Afghanistan, Iraq, and Syria.

That’s about a 3 percent increase in inflation-adjusted dollars over what the Obama administration would have been expected to request in its final Future Years Defense Program.

“For the years after 2018, CBO estimates the Administration’s goals for the military would result in steady increases in costs so that by 2027, the base budget (in 2018 dollars) would reach $688 billion, more than 20 percent larger than peak spending during the 1980s,” the report said.