Thirty-five countries pledged Tuesday to turn international guidelines on nuclear security into national laws, a move aimed at preventing terrorists from getting their hands on nuclear material.

Tuesday's initiative following a two-day summit of leaders also commits countries to open up their security procedures to independent review, a further step toward creating an international legal framework to thwart nuclear terrorism, said a joint statement from the Netherlands, the United States and South Korea.

U.S. Energy Secretary Ernest Moniz said the guidelines are now ``the closest things we have to international standards for nuclear security.''

In a closing communique, all 53 countries that participated in the Nuclear Security Summit in The Hague agreed to keep looking for ways to ensure nuclear material doesn't fall into the hands of terrorists.

But the agreement on adopting guidelines into law was endorsed by just 35. Among other countries that agreed were France, Britain, Canada and Israel; notably absent were Russia, China, India and Pakistan.

``We need to get the rest of the summit members to sign up to it, especially Russia, and we need to find a way to make this into permanent international law,'' said Miles Pomper of the James Martin Center for Nonproliferation Studies.

Over the course of three summits since U.S. President Barack Obama launched the series in 2010, the number of countries that have enough material to build a nuclear weapon has fallen from 39 to 25.

This summit featured new reduction commitments, with Japan, Italy and Belgium pledging to reduce their stocks of highly enriched uranium and plutonium.

Other groups of nations have pledged to increase efforts to combat illicit trafficking in nuclear material, boost maritime security and to develop low-enriched uranium for research reactors instead of the highly enriched, weapons-grade nuclear fuel currently widely used.

The closing accord also included a note on the need for countries to consider the potential threat posed by cyberterrorism.

European Commission President Jose Manuel Barroso said the summit was crucial at a time when ``international stability and security are being put into question in a very serious manner'' _ a clear reference to the Ukraine crisis.

``It is therefore all the more important to show that we are united in our commitment to a multilateral order based on peace and the unequivocal respect of the rule of law,'' he said.

Michelle Cann of the Partnership for Global Security said Tuesday's deal was significant because it marks ``a change in the way security is done.''

Cann said the gains from reducing nuclear material would likely trail off in the future and the most important thing remaining that can be done to improve security is for groups of like-minded countries to lead the way.

Because of the difficulty of getting countries to agree to an international treaty, creating a package of ``best practices'' and goals for countries to achieve should create peer pressure among nations, with none wanting to be seen as the most lax at safeguarding their nuclear material.

Agreeing to external checks, conducted under the auspices of the IAEA, is especially important.

``We've had these countries participating in this process for six years, and now we only have two-thirds of them willing to say `yes, I'm going to fully implement the International Atomic Energy Agency's fundamental recommendations on how to safeguard this material,''' said Cann. (AP)