The Navy’s oft-stated goal of a 313-ship fleet should be considered a minimum level that may have to be increased to meet obligations around the world, the Navy’s top admiral said Tuesday.

Adm. Gary Roughead, chief of naval operations, suggested the fleet will have to grow to meet the Navy’s commitments. “The 313 will not be enough for the missions that we’re going to be tasked with in the coming years,” he said.

Roughead’s remarks after touring Navy shipbuilder Bath Iron Works and submarine repair yard Portsmouth Naval Shipyard follow a briefing issued by another admiral before Thanksgiving that indicated the 313-ship goal may be adjustable.

The briefing paper by Vice Adm. John Morgan laid out three scenarios, including one that would reduce the fleet and two that would increase the number of ships, to 474 and 534 ships, respectively. The Navy’s fleet currently stands at 280 ships.

Shipbuilders who’ve trimmed their work forces because of tight shipbuilding dollars would welcome a larger fleet but Roughead didn’t offer any specifics on how many more ships would be needed, or what type of ships will need to be built.

Roughead’s visit came as Bath Iron Works negotiates with the Navy for the final contract to build the first next-generation DDG-1000 Zumwalt destroyer and as Portsmouth Naval Shipyard makes preparations to overhaul Virginia-class submarines.

As it stands, the Navy intends to build seven of the Zumwalt-class destroyers and 55 smaller Littoral Combat Ships designed for nearshore operations. Roughead stuck with those numbers in an interview with reporters.

Maine was the first stop on Roughead’s tour of Navy shipbuilders. The next stop is the Austal shipyard in Alabama where one of the versions of the LCS is being built. Bath Iron Works is lead contractor on that project.

From there, he visits Northrop Grumman’s Ingalls, Gulfport and Avondale shipyards in Mississippi and Louisiana before traveling to National Steel and Shipbuilding Co. in San Diego. He wraps up the tour with a visit to the Marinette Marine shipyard in Wisconsin where the other Littoral Combat Ship version is being built.

Roughead reiterated that the speedy Littoral Combat Ship that’s designed to go where larger ships can’t is an important program. He said other countries are watching the program and may be interested in acquiring the ships once the Navy settles on a design.

He declined to say whether one program is more important than another when it comes to aircraft carriers, amphibious assault ships, destroyers, submarines and other Navy ships. He said the Navy is seeking “a balanced fleet.”

It was Roughead’s first visit to Bath since 2001 when he was chief of the Navy’s office of legislative affairs, before completion of the $300 million land-level transfer facility designed to make the Navy shipbuilder faster and more efficient.

The shipyard also is in the process of building a 66,788-square-foot “Ultra Hall” to allow shipbuilders to put together larger hull segments in an enclosed, climate-controlled facility. The project is key to construction of the Zumwalt destroyer, which will be much larger than destroyers currently built in Bath.

Roughead said he was impressed with the shipyard improvements, the attitude of Bath workers and the shipyard’s ability to reduce costs. “That gives me optimism with respect to being able to increase our shipbuilding program,” he said.

Before touring Bath Iron Works, Roughead received a similar familiarization tour of Portsmouth Naval Shipyard in Kittery.

The shipyard, spared in the last round of base closings, has focused for years on the repair and overhaul of Los Angeles-class attack submarines. Its workers have begun training to begin work on newer Virginia-class subs down the road.

Roughead’s travel plans underscored the changing landscape of the defense infrastructure in the region. He flew into Pease Air National Guard base, which was closed in 1991 as a part of federal budget cutting measures, for his visit to Portsmouth Naval Shipyard.

For his visit to Bath Iron Works, he used the airstrip at the Brunswick Naval Air Station, which is due to close by 2011, where he met with reporters before departing.

Roughead’s visit came after a weekend incident in which Iranian fast boats swarmed U.S. ships in the Persian Gulf, but Roughead opted to continue with his tour of shipyards this week.