PRAGUE — On April 8 in Prague, Russian President Dmitry Medvedev and U.S. President Barack Obama signed a new strategic arms reduction treaty (START). That agreement is an historic achievement and an inspiration for further progress in global arms control. But at the same time, here and now, we must also prepare to defend against another, less encouraging trend.

The proliferation of weapons of mass destruction and their means of delivery is a threat to both the NATO allies and Russia. A look at current trends shows that more than 30 countries have or are developing missile capabilities. In many cases, these missiles could eventually threaten Europe's populations and territories.

Iran is a case in point. It has signed the Nuclear Nonproliferation Treaty, and is developing a nuclear program that it claims is for civilian purposes only. But Iran has gone far beyond what is necessary for a purely civilian program. It has concealed several nuclear facilities from the International Atomic Energy Agency, played hide-and-seek with the international community and rejected all offers of cooperation from the United States, the European Union and others. Most recently, Iran's government announced plans to enrich its uranium to levels that appear incompatible with civilian use and that defy several United Nations Security Council resolutions.