Groton — The commissioning of the $2.6 billion submarine that will become USS North Dakota has been postponed because of issues with the design of the bow and component parts, the Navy said Wednesday.

The attack submarine was christened Nov. 2 at Electric Boat. It had been scheduled to join the fleet with a commissioning ceremony May 31.

Colleen O’Rourke, a Washington-based spokeswoman for Naval Sea Systems Command, told the Associated Press that the cause of the problems remains under investigation, and it is not clear which contractor might be responsible. A new date for the commissioning ceremony has not been set.

EB spokesman Robert Hamilton said Wednesday that Electric Boat expects to complete the submarine within the 66-month time frame of the contract with the Navy, “the shortest contract schedule of any Virginia-class submarine to date.” Construction of the submarine started March 2, 2009, and the contract calls for delivery by Aug. 31, Hamilton said.

He referred questions about the delay in the commissioning of the submarine to the Navy.

The North Dakota (SSN 784) is the first submarine to have a redesigned bow with a new sonar array and two larger payload tubes instead of 12 individual, vertical-launch missile tubes. Twenty percent of the ship’s design was changed to save about $100 million per submarine. Virginia-class boats cost about $2.6 billion each.

“This decision is based on the need for additional design and certification work required on the submarine’s redesigned bow and material issues with vendor-assembled and delivered components,” the Navy said in a news release.

At the christening ceremony in November, Vice Adm. Michael J. Connor, commander of the submarine force, said he previously had seen the North Dakota’s “highly innovative bow section” during a tour of the Newport News shipyard.

“Now it’s great to see it all put together,” Connor said at the time.

The 377-foot-long submarine will be able to launch Tomahawk cruise missiles, deliver special forces and carry out surveillance over land and sea.

The ship, the 11th member of the Virginia class, was scheduled to undergo sea trials after the christening and to be delivered to the Navy as early as the end of February, according to Kurt A. Hesch, Electric Boat vice president and program manager for the Virginia-class submarines. In November, the North Dakota was on track to be delivered after 59 or 60 months of construction, six or seven months sooner than called for in the Navy contract.

Electric Boat in Groton and Newport News Shipbuilding in Virginia build two Virginia-class submarines a year together. EB previously delivered the USS Mississippi to the Navy in 62 months, and Newport News built the USS Minnesota in 63 months.

The submarine is the second Navy vessel to be named North Dakota. The last ship named for the state was a coal-fired, steam-powered battleship built in 1910. It was decommissioned in 1923 and sold for scrap in 1931.