GROTON, Conn. >> With U.S. attack submarines sidelined by extended delays at government shipyards, the Navy is turning to private companies to perform more of the maintenance work on the nuclear-powered vessels.

The commander of the Navy’s submarine force, Vice Adm. Michael Connor, said routine overhauls that once took 19 months have been taking 28 months because of staffing shortages at U.S. shipyards brought about by federal budget cuts.

"That has a significant impact on the force," Connor told The Associated Press in an interview.

The companies expected to bid on new contracts for overhaul work are Electric Boat, a Groton-based division of General Dynamics, and Virginia’s Newport News Shipbuilding, a division of Huntington Ingalls Industries, Connor said. He said the work could help protect the industrial base at the two private submarine builders prepare for work on a new class of ballistic-missile submarines.

The country’s four Naval shipyards, which employ about 30,000 people, have been understaffed because of automatic Pentagon budget cuts and a civilian hiring freeze that took effect just as many submarines came due for refueling or major overhauls, according to Chris Johnson, a Naval Sea Systems Command spokesman. Although the hiring freeze was lifted in June 2013, Johnson said the shipyards are not expected to be fully manned until the end of fiscal year 2016.

At the Portsmouth Naval Shipyard in Maine, which overhauls attack submarines, officials said last month they were hiring more than 700 workers. The Navy says its other shipyards — in Virginia, Hawaii and Washington state — are also recruiting and hiring aggressively.

As the shipyards cope with excess demand, top Navy officials have assigned first priority among nuclear-powered vessels to ballistic-missile submarines and aircraft carriers, leaving attack submarines in what Connor called a distant third. He said he asked for Naval Sea Systems Command to look toward the private sector.

"We need the capacity of the country to be sufficient to keep these very valuable ships at sea as much as they’re intended to be at sea," Connor said Thursday during a talk at a veterans’ hall in Groton.

The Naval Submarine Base in Groton is the Navy’s primary homeport on the East Coast for attack submarines, which are equipped to conduct covert surveillance, attack targets with Tomahawk cruise missiles, launch special forces and hunt other ships and submarines.

The Navy has more than 50 attack subs, a number that has been declining since the end of the Cold War. A new construction program will reverse that trend in years ahead but, in the meantime, the military has at times extended standard six-month deployments to help meet demand from commanders.

Loren Thompson, an analyst at the Lexington Institute, a defense-oriented public policy advocacy group, said a big shift in workload to the private sector could face opposition from unions at the public shipyards and local congressional delegations, which may fear losing the jobs permanently. But he said there are strong arguments for outsourcing.

"It makes sense to do more of the maintenance in the same place where the submarines are built because the people there understand the boats best," he said.

Johnson said he could not say exactly how much additional work might be contracted out to private shipyards.

At Electric Boat, spokesman Dan Barrett said the company is completing maintenance and modernization efforts on one attack sub and is reviewing a request for proposals that the Navy has issued for work on two others.