United Nations - Delegates from the United States, United Kingdom and France walked out Monday as Iranian President Mahmoud Ahmadinejad blasted the US and Israel at a global gathering on disarmament. Ahmadinejad is rejecting allegations his country is developing nuclear weapons, citing "not a single credible proof." Ahmadinejad is condemning the continued possession of nuclear weapons by the United States and others. He spoke Monday at the start of a monthlong conference reviewing the Nuclear Nonproliferation Treaty. He says such atomic weapons are an encouragement to other countries to develop similar arsenals. He is calling for a timetable for elimination of nuclear arms worldwide. Such threats should meet with "swift reaction from the United Nations and termination of all cooperation of NPT member states with the threatening aggressor state," Ahmadinejad said. The delegations of the United States, Britain and France all walked out of the UN General Assembly chamber during the Iranian president's speech. Among the punishments that should be meted out to countries that use, or threaten to use, atomic weapons against other nations is suspension from the board of governors of the UN nuclear watchdog in Vienna, Ahmadinejad said. The United States' so-called nuclear posture review reduces the role of atomic weapons in US defense policy but does not rule out the use of nuclear warheads against countries like Iran and North Korea that are considered to be NPT violators. Both the United States and Israel have suggested that they could use military force against Iranian nuclear facilities, which they suspect are part of a covert atomic weapons program. Iran denies pursuing atomic weapons and insists its nuclear ambitions are limited to peacefully generating electricity.