General Dynamics NASSCO, a primary constructor of ships for the U.S. Navy, warned about 1,040 employees on Monday that indefinite layoffs may come in late April due to uncertainty created by the U.S. budget cuts .The U.S. Worker Adjustment and Retraining Notification Act (WARN) requires most companies with 100 or more employees to give notification 60 days in advance of mass layoffs or plant closings.Military contractors are the hardest hit by the cuts because a large part the reductions are expected to come from Defense Department spending.