Senior international officials are marking the 20th anniversary of the treaty banning nuclear testing and the U.N. organization created to enforce it with calls for holdout nations to bring the pact into force by ratifying it.

The Comprehensive Test Ban Treaty Organization already polices the world for any sign of nuclear tests. But it still cannot go on site to inspect for tests.

That can happen only if the treaty enters into force. And that will happen only if the holdouts among the 44 countries that are designated "nuclear capable" — the United States, China, Egypt, India, Iran, Israel, North Korea and Pakistan — ratify.

EU foreign policy chief Federica Mogherini and U.N. Secretary General Ban Ki-moon were among those urging the international community Monday to push for full ratification.