WASHINGTON – The Justice Department filed suit Tuesday to block the proposed acquisition of Newport News Shipbuilding Inc. by General Dynamics Corp., saying the merger would result in a monopoly for building nuclear submarines, a weapon vital to national security.

The department said the proposed acquisition would harm competition for other military ships and for the development of technology for powering nuclear submarines.

The Department of Defense had significant competitive concerns about the transaction and worked with Justice in an investigation that led to the lawsuit, the Justice Department said.

General Dynamics, the parent company of Bath Iron Works, had planned to acquire a controlling share of Newport News for $2.6 billion.