WASHINGTON, May 28 — The Pentagon is pressing Congress to approve the development of a new weapon that would enable the United States to carry out nonnuclear missile strikes against distant targets within an hour. The proposal has set off a complex debate about whether this program for strengthening the military's conventional capacity could increase the risks of accidental nuclear confrontation. The Pentagon plan calls for deploying a new nonnuclear warhead atop the submarine-launched Trident II missile that could be used to attack terrorist camps, enemy missile sites, suspected caches of biological, chemical or nuclear weapons and other potentially urgent...