ZAO, Japan – Japanese military helicopters dumped loads of seawater onto a stricken nuclear reactor Thursday, trying to avoid full meltdowns as plant operators said they were close to finishing a new power line that could restore cooling systems and ease the crisis.

U.S. officials in Washington, meanwhile, warned that the Fukushima Dai-ichi plant in northeastern Japan may be on the verge of spewing more radioactive material because water was gone from a storage pool for spent nuclear fuel rods.