The U.N. Security Council has approved a resolution urging quick global implementation of a treaty that would ban tests of nuclear weapons.

U.S. Secretary of State John Kerry invoked North Korea's latest nuclear explosion In urging ratification of the treaty for "a safer, more secure, and more peaceful planet."

But the U.S. has not yet done so. Anti-treaty minded Republicans rejected it under President Bill Clinton and congressional opposition remains strong today.

The U.N.'s Comprehensive Test Ban Organization already has a network of monitoring stations. But it still cannot go on site to inspect for tests until the treaty enters into force. For that, the holdouts among the 44 countries that are designated "nuclear capable" — the United States, China, Egypt, India, Iran, Israel, North Korea and Pakistan — ratify.