Representatives from nuclear powers China and Russia are among those scheduled to address the Nuclear Non-Proliferation Treaty conference at the United Nations Tuesday.
The United States has been engaged in negotiations with both countries on a plan to possibly impose another round of U.N. sanctions on Iran to pressure the country to stop enriching uranium.
Meanwhile, Iranian President Mahmoud Ahmadinejad has canceled a news conference he had planned to hold at the U.N. on Tuesday, a day after he told conference delegates that U.S. production of nuclear weapons had encouraged other nations to produce weapons.
He instead plans to hold an invitation-only meeting with selected media at his New York hotel on Tuesday.
Earlier Tuesday, Iran called for independent verification of a U.S. disclosure concerning the size of its nuclear arsenal. Foreign Ministry spokesman Ramin Mehmanparast also questioned if the U.S. is "justified" in having stockpiled more than 5,000 nuclear warheads.
His comments were in response to the Pentagon's announcement Monday that the U.S. has 5,133 nuclear warheads, which represents an 86-percent decline since the late 1960's.
On Monday, U.S. Secretary of State Hillary Clinton issued a strong condemnation of Iran, saying the country will do whatever it can to divert attention away from its own record to evade accountability, and that Iran's nuclear ambitions put the world at risk.
Speaking at the conference, Clinton called for introducing automatic penalties for noncompliance with the treaty, rather than relying on diplomacy to impose penalties.
Iran is a signatory to the Nuclear Non-Proliferation Treaty, which is designed to check the spread of atomic weapons worldwide. However, the United States accuses Iran of secretly working to produce a nuclear weapon. The U.S. and its allies are seeking a fourth set of U.N. sanctions to pressure Iran to stop enriching uranium.
Iran says its enrichment program is for peaceful purposes.
The 189 signatories to the Nuclear Non-Proliferation Treaty gather every five years to discuss compliance and strengthening the treaty, which aims to halt the spread of nuclear weapons. The conference in New York ends May 28.