"Today, 50 years later, we celebrate the immeasurable contributions this landmark treaty has made to the security and prosperity of the nations and peoples of the world," the nuclear powers' foreign ministers said in a joint statement.

"We reaffirm our commitment to the NPT in all its aspects," the ministers added, saluting the "immeasurable contributions this landmark treaty has made to the security and prosperity of the nations and peoples of the world" since it entered force on March 5, 1970, two years after its signing.

"The NPT has provided the essential foundation for international efforts to stem the looming threat -- then and now -- that nuclear weapons would proliferate across the globe. In so doing, it has served the interests of all its parties," the ministers stated.

They underlined their support for the International Atomic Energy Agency (IAEA) for its "critical role in NPT implementation, both to promote the fullest possible cooperation on the peaceful uses of nuclear energy, and to apply safeguards and verify that nuclear programs are entirely peaceful."

Tuesdays statement came a week after the IAEA expressed concern and demanded "clarifications" from Iran over an undeclared site in Tehran where uranium particles were found late last year.

The IAEA has for months been pressing Tehran for information about activities being carried out at the undeclared site where the particles were found.

The nuclear powers did not mention Iran in their statement, stating only their commitment under the NPT to "the pursuit of good faith negotiations on effective measures related to nuclear disarmament" while supporting "the ultimate goal of a world without nuclear weapons with undiminished security for all."

They added that the benefits of nuclear energy had to reside in "applications for peaceful purpose."

The foreign ministers of the five powers warned that "the success of the NPT was not foreordained, nor is its future success guaranteed. It depends on our concerted and sustained efforts to ensure compliance, to promote universalisation, to ensure effective safeguards, and to respond to ongoing and emerging proliferation challenges, wherever they occur.

"Even at the height of the Cold War, our predecessors made this wise investment in our shared security and prosperity. Today, we pledge our unstinting commitment to preserving and deepening this legacy for future generations," the ministers concluded.