The controversial left-winger made the claim at a news conference with London Mayor Ken Livingstone, stating his belief that any such attack would be "madness".

But speaking at London's City Hall, the seat of the British capital's municipal government the Greater London Authority, Chavez insisted he does not believe the Islamic Republic was seeking a nuclear capability.

"We want dialogue, we are not for war. All we want is respect for the will of the people of Iran," he added.

But he said of any military action against Tehran: "I know you men and women in London, whatever you are paying for a gallon of petrol, it would be more.

"The situation would be destabilised against the whole world and that is why we want peace."

Chavez, whose whistlestop visit to Britain does not include a meeting with Prime Minister Tony Blair or any government members, also launched into a now characteristic attack on US President George W. Bush.

When one BBC journalist sought to compare him with Bush for interfering in the affairs of other countries, he responded: "If you are going to compare me to the worst criminal in humanity -- the president of the US -- he is an assassin; he is a criminal responsible for genocide, completely immoral.

"I believe that he should be put in jail. He has invaded a country. Are we bombing cities?"

The comments followed on from his speech soon after arriving Sunday in which he denounced the international community for not standing up to the "American empire" and in which he said Iraq was the "Vietnam of the 21st century".

Livingstone, an often off-message member of Blair's governing Labour Party whose socialist views earned him the nickname "Red Ken" in the 1980s, said: "I sometimes have views on George Bush not too dissimilar from yours."

The mayor, who threw a lunch for Chavez with a string of leftist guests and sympathetic lawmakers, has defended the ex-military man as "the best news out of Latin America in many years".

Chavez's relations with Blair have deteriorated since their warm embrace in London in 2001, with the Venezuelan leader recently denouncing the British premier as "the main ally of Hitler" for supporting Bush.

The trip, part of a tour of Europe and Africa, was designed to establish stronger economic links with the Latin American country which Chavez has led since 1998 after a previous failed coup attempt in 1992.

Chavez's social reforms have earned him a groundswell of support from his fellow countrymen, but some Venezuelan dissidents and human rights groups have complained of violence and oppression against political opponents.

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