(CNN) - Three of the Navy's nuclear-powered attack submarines are "not certified to dive today" due to maintenance delays caused by overcrowded shipyards, officials revealed Wednesday.
During a Senate Armed Services Committee hearing, Vice Chief of Naval Operations Adm. William Moran told lawmakers that one of the submarines, the USS Boise, will finally enter a shipyard in January after being out of service for four years.
Two additional attack submarines are currently not operational and will go into dry dock in the new year for repairs, according to Moran.
The Navy has been working to address its backlog of submarines, with some forced to wait years for maintenance, and has leaned on using private shipyards, in addition to public ones, to help speed up the process.
But while the service has taken steps to address maintenance challenges that have at times sidelined a significant chunk of its submarine fleet, Navy officials testified Wednesday that more work is needed.
"We've aggressively gone after readiness challenges in our operational submarine fleet, and identified three key drivers: public shipyard capacity, shipyard productivity and parts availability," Moran told lawmakers.
"Working with our industry partners, we've been able to allocate multiple submarines to private shipyards in order to alleviate the disparity between demand and capacity within our public shipyards. Our first-ever Shipyard Infrastructure Optimization Plan, delivered to Congress earlier this year, establishes our road map to upgrade our dry docks, facilities and equipment to improve overall productivity," he said.
However, a new report released Wednesday by the Government Accountability Office indicates that the problem is getting worse, not better.
Since 2012, Navy submarines have been sidelined for an additional 7,321 days because of maintenance delays, according to the report.
"The Navy has developed a plan to improve shipyards and is re-examining its ship manning, among other actions; however, these positive steps have not yet fully addressed GAO's recommendations," the report says, adding that additional resources will likely be needed to address the problem, if the service hopes to follow through with its plan to grow the fleet.
In the short term, Navy officials hope to avoid waiting years for a submarine to be repaired, as they did with the USS Boise.
"We want no more Boises," Moran told senators, noting that "the numbers are coming down significantly."
"The standing in line has come down significantly," he added. "We still have a ways to go. We're not out of the woods yet, but I think as capacity opens up in the private yards, and we do a better job in the public yards, getting our carriers out on time, we'll be there."
Despite President Donald Trump's request for additional defense spending, years of budget cuts and continuing resolutions have had a severe impact on the Navy's maintenance and shipbuilding efforts.
On Wednesday, Sen. Mike Rounds made it clear that Americans need to understand the severity of the problem, particularly if the government should come under mandatory budget cuts called sequestration, as it last did in 2013.
"It appears to me, even with the resources we've allocated so far, we are going the wrong direction," the South Dakota Republican said, regarding the current submarine fleet.
"If it's a matter of resources, and you are not here in a public testimony to tell us what the impacts of not having the additional resources necessary to keep these critical pieces in the defense of our country operational, how in the world can we ever go to what we know we need in a 355-ship Navy and support them if we can't communicate to the American people how critical it is to maintain the defense posture we currently got?" Rounds added.
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