Tehran's UN envoy has accused the United States of denying Iran's first vice president and members of his delegation visas to attend a UN conference on the global financial crisis.

'I am indeed delivering this speech on behalf of Dr. (Parviz) Davoudi, first vice president of the Islamic Republic of Iran, who along with members of the Iranian delegation was not able to participate in the conference,' Iranian UN ambassador Mohammad Khazaee told the UN General Assembly.

'Their entry visas were not issued by the host country,' he added, referring to the United States.

It was not clear whether the alleged visa denial was related to the Iranian government's crackdown on demonstrators who protesting against what they say was a rigged presidential election in which hardline president Mahmoud Ahmadinejad was declared the winner.

A US official said he was looking into the allegation. Washington cut off diplomatic relations with Tehran in 1980, five months after Iranian militants stormed the US Embassy in Tehran. They held 52 Americans captive for 444 days.

As host country of the UN Secretariat in New York, Washington has followed a policy of issuing visas for members of UN delegations, in line with a 1947 pact with the United Nations, regardless of disputes with individual countries.

However, it does sometimes refuse entry to Iranian government officials and professionals.

Venezuelan ambassador Jorge Valero Briceno told the conference his country's chief delegate, Finance minister Ali Rodriguez, also had problems with his visa because the US embassy in Caracas had 'created obstacles.'

'This is not the first time that such an event has taken place with a high official of the Bolivarian (Venezuelan) government,' he said.

An official at the Venezuelan mission said Rodriguez was expected to arrive later on Friday. Originally Venezuela's left-wing president Hugo Chavez had been scheduled to attend but later decided to send Rodriguez.-Reuters