The Navy will need about $9 billion more in its annual shipbuilding budget to grow the fleet to 350 ships, close to the size needed according to a new force structure assessment released last month and matching President-elect Trump's vision for the service.

The Navy has spent $15.9 billion in its shipbuilding account each year over the past 30 years on average, according to a report released this week from the Congressional Budget Office. But building and maintaining a fleet of 350 ships, close to the 355 requested by the assessment, would cost $25 billion per year, about 60 percent more than the historical average, the report said.

The Navy's force structure assessment found that the Navy needs to grow from 308 to 355 ships to better counter threats from Russia and China. The proposed build-up includes an additional aircraft carrier and more large warships and attack submarines. The fleet has 274 ships now.

President-elect Trump also called for a fleet of around 350 ships during the presidential campaign.

"My plan will build the 350-ship Navy we need," Trump said in an Oct. 21 speech. "This will be the largest effort at rebuilding our military since Ronald Reagan, and it will require a truly national effort."

But doing so will require Congress to undo the Budget Control Act and lift the sequestration caps that have limited how much can be spent on defense, as well as other federal priorities. If the caps remain in place, and the Navy allocates the same portion of its budget to shipbuilding as it has in the past, the annual shipbuilding budget would be 20 percent short of reaching the Navy's 2017 plan, which would purchase 254 ships over the next 30 years.