Ali Asghar Soltanieh, a key member of the Iranian team engaged in negotiations with world powers over Tehran's controversial nuclear programme, also accused Washington of being the "real" threat to global peace given its large nuclear arsenal.
"The outcome of the Washington conference is already known. Any decision taken at the meeting is not binding on those countries who are not represented at the conference," Soltanieh told ISNA news agency.
US President Barack Obama was later Monday to open the nuclear security summit which is being attended by leaders of 46 other countries.
Iran, which is at loggerheads with the United States over its atomic programme, is not represented at the conference.
But the US State Department has said that efforts to pressure Iran to give up its nuclear programme will be a "significant" topic during the meeting.
Iran has been under mounting global pressure to abandon its nuclear programme, with Western powers fearing it wants to build an atomic bomb. Tehran says the programme is peaceful and only meant to produce energy.
Iran has already been slapped with three sets of United Nations Security Council resolutions, and the spectre of more looms, spearheaded by Washington and some western nations.
The two-day Washington summit aims to raise issues of safeguarding unsecured uranium and separated plutonium stockpiles and averting the nightmare scenario of extremist groups acquiring nuclear weapons.
Soltanieh said it was Washington that was "the real threat to international security with its nuclear weapons."
"The new US (nuclear) policy proves Islamic Republic of Iran's argument that the US is not committed to any global rules and regulations," he said referring to Washington's latest nuclear policy unveiled last Tuesday.
Top Iranian officials led by supreme leader Ayatollah Ali Khamenei have expressed deep anger at the policy, which limits Washington's use of its nuclear arsenal but singles out Iran and North Korea as exceptions.
Iran, meanwhile, will hold its own two-day nuclear disarmament conference on April 17 and 18.
Iran is yet to unveil the list of participants attending its conference but officials say delegations from the UN nuclear watchdog and the UN would be attending.
