Iran's nuclear program poses the greatest threat to the credibility of the global pact aimed at halting the spread of atomic weapons, a senior U.S. arms control official said on Monday.
The Islamic Republic has a "long history" of deceiving the International Atomic Energy Agency (IAEA) and its nuclear enrichment program far exceeds that needed for civilian use, said Thomas Countryman, Assistant Secretary for International Security and Nonproliferation.
Two-week talks that opened in Geneva on Monday to review progress in implementing the nuclear Non-Proliferation Treaty (NPT) were taking place in a difficult environment, he said.
North Korea, which is not attending the global talks having announced its withdrawal from the treaty a decade ago, presents a "dangerous challenge to regional peace", he said. North Korea conducted its third test of a nuclear weapon in February.
"The actions of Iran and North Korea should concern every member of this conference," Countryman told a news briefing.
"It is clear that if Iran succeeds in the project of constructing nuclear weapons, then it is not only the Helsinki meeting that becomes irrelevant, but it is in fact the entire credibility of this treaty."
Countryman was referring to a decision last November to put off talks on banning atomic bombs in the Middle East that were due to have taken place in Helsinki in December.
Iran blamed the United States at the time for a "serious setback" to the NPT.
"The possession of such weapons by Iran constitutes a threat to the entire region and an impetus for greater proliferation, lateral proliferation of weapons, than we have ever seen."
Iran's acquisition of a nuclear weapon would be a "genuine tipping point and would cause more damage to the treaty than anything else that has occurred in its history", he added.
Mohammad-Mehdi Akhondzadeh, Iran's deputy foreign minister, addressed the talks on Monday on behalf of the Non-Aligned Movement of developing nations and reaffirmed the right of all nations to develop nuclear energy for peaceful purposes.
The U.N. nuclear agency, the IAEA, is talking with Iran to set a date for discussions on resuming an investigation there, it said on Monday.
The IAEA-Iran talks are separate from, but have an important bearing on, diplomatic negotiations between Tehran and six world powers aimed at a broad settlement to the decade-old dispute and reduce the risk of a new Middle East war.
"We remain committed to seeking a diplomatic solution with the Iranians for as long as that remains possible, but at the same time using the tools of diplomacy which include talking in order to show the Iranians that the world is united in its demand that they come back into compliance with their obligations," Countryman said.
The European Union, in its address to the NPT talks, voiced concern at "current non-proliferation challenges" in North Korea and Iran, as well as in Syria, specifically long-standing suspicions linked to Deir al-Zor and other sites.
The EU said it aimed to reach a comprehensive long-term settlement to restore international confidence in the exclusively peaceful nature of Iran's nuclear program, ensuring Tehran's compliance with its obligations under the NPT as well as Security Council and IAEA resolutions.