KITTERY — Portsmouth Naval Shipyard has begun hiring more than 700 workers to deal with an increase in work as the Navy aims to reduce maintenance delays on its fleet of nuclear submarines, officials said Thursday.

The hiring of 715 workers will boost the shipyard workforce from 4,700 to 5,200 civilian employees, once attrition is factored in, said Capt. William Greene, shipyard commander.

Recruiting is already underway with a goal of completing the hiring by the end of September. The shipyard will be hiring more than 100 engineers and about 25 administrative personnel. The remainder will be trades-oriented jobs like shipfitters, fabricators, machinists, pipefitters, and electricians.

The head of the Naval Sea Systems Command said in October that budget sequestration had contributed to maintenance delays for the Navy’s fleet of nuclear submarines, especially attack submarines like those overhauled at Portsmouth Naval Shipyard.

The Portsmouth Naval Shipyard, located on an island in Kittery, Maine, has a military and civilian payroll of more than $450 million. The shipyard’s civilian workforce is divided roughly evenly between Maine and New Hampshire.

The shipyard expects to see an increase in maintenance work this year, and possibly in the coming year, said Paul O’Connor, president of the Metal Trades Council, the largest union at the shipyard.

Mandated budget cuts necessitated by sequestration only added to a backlog of work — and served to drive up costs through overtime and deferred maintenance, he said. “We need prudent, sensible budget modifications — not this wholesale slashing. It might sound good for someone running for re-election, but it doesn’t play out well for taxpayers,” he said.