国际英语新闻:Obama Hails Summit Accord, But Says Nuclear Terrorism Still a Risk

During six years of international meetings on nuclear security, which he initiated, the U.S. president said, "We’ve embraced a new type of thinking and a new type of action."

"This is a perfect example of a 21st-century security challenge that no one nation can solve alone," Obama said at the summit's plenary session Friday. "It requires coalitions and sustained coordination across borders and institutions."

He also met with a smaller gathering of the nations mostly closely involved in last year's nuclear agreement with Iran. Obama said that deal was "a substantial success ... focused on the dangers of nuclear proliferation in a real way."

Nuclear sites' security

One U.S. lawmaker, Congressman Ed Royce, chairman of the House Foreign Affairs Committee, said, "We should assume terrorists will continue to seek out the weakest links at nuclear facilities around the globe."

World leaders also are concerned about the security of nuclear materials and facilities in countries such as nuclear armed Pakistan, where a terrorist attack in Lahore last Sunday killed more than 70 people, many of them Christians celebrating the Easter holiday.

Experts say security gaps remain for several reasons: there still is no international framework to monitor nuclear materials; some countries are unwilling to open up supplies intended for commercial use, and some militaries have been unable to agree on how to deal with their nuclear material.

"If you wanted to cause a nuclear incident, you might look for the country with the most vulnerable reactors," said James Andrew Lewis, head of the Strategic Technologies Program at the Center for Strategic and International Studies.