Faced with mounting pressure over his country's atomic ambitions, Iranian President Mahmoud Ahmadinejad left on a five nation tour Sunday, including Brazil in a bid to boost ties with Latin America's biggest economy and a rare backer of Tehran's nuclear programme.

Since coming to power in 2005, Ahmadinejad has sought to form bonds with leftist south American leaders, and enjoys "brotherly ties" with fiercely anti-US Hugo Chavez, president of Brazil's neighbour, Venezuela.

His five-day trip will also take in Venezuela as well as another left-leaning South American country, Bolivia and the West African countries of Senegal and Gambia, the presidential website said.

"Nations such as Iran, Brazil, Venezuela, Gambia and Senegal have the ability to restore a new world order," Ahmadinejad said before leaving Tehran.

Highlighting Tehran's growing ties with Brazil, the hardliner said: "Iran and Brazil have a common vision about the situation in the world and are determined to develop their cooperation."

The Islamic republic's influence in arch-foe the United States' back yard has unnerved Washington and its key Middle Eastern ally Israel amid speculation Venezuela and Bolivia might be providing uranium to Iran for its controversial nuclear programme.

Brazilian President Luiz Inacio Lula da Silva has backed Iran's nuclear development programme as long as it is peaceful, as Brazil seeks to up its diplomatic profile by playing a mediating role in the Middle East.

Lula, who hosted Israeli President Shimon Peres earlier this month, is firmly against sanctions on Iran over its nuclear defiance and has called for diplomacy and talks.

Israel accuses Iran of seeking atomic bombs and along with the United States has never ruled out a military option to thwart the nuclear drive. Iran denies it seeks atomic weapons.

The West is currently hoping to receive a positive response from Iran on a UN-brokered nuclear deal aimed at allaying their fears that Iran could use its enriched uranium to make a bomb.

In an interview with AFP in September, Lula said he believed US-led criticism of Iran was reminiscent of Washington's fallacious justification for the war in Iraq.

"Even today, those leaders in favour of the war in Iraq are unable to explain why they invaded if there were no chemical weapons. Well, I am seeing the same sort of things starting to happen over Iran," he said.

Iran is already under three sets of UN sanctions over its refusal to suspend uranium enrichment.

Ahead of the visit, Ahmadinejad welcomed Brasilia's support for Tehran's nuclear drive.

"While there is an unfair polemic in Western countries against Iran's peaceful nuclear programme, the people of Brazil side with the Iranian people," Ahmadinejad said in a statement.

"If the Brazilian people and the Iranian people are united on issues such as the Zionist regime's cruel attack on the defenceless people of Gaza, this will show a mutual desire" for peace, he added.

During the visit Ahmadinejad is expected to discuss cooperation in the areas of technology, oil production and space exploration.

In his trip to Bolivia, which sits on South America's second largest gas reserves, Ahmadinejad and his counterpart Evo Morales will hold a private meeting and sign bilateral agreements, La Paz has said.

And in Venezuela, the Iranian hardliner is expected to receive a warm welcome given his good relations with Chavez, as the two leaders are known for their populist economic policies and strong anti-US tirades.

Chavez, who also supports Tehran's nuclear programme, has himself been a regular visitor to Iran since the presidency of Ahmadinejad's predecessor Mohammad Khatami, the reformist president.

Since his disputed re-election in June, Ahmadinejad has been dogged by mass protests by opposition supporters charging the polls were rigged, and the regime has come under fire abroad for its violent suppression of protests.

Ahmadinejad has also faced criticism at home by his political rivals over the benefits of seeking allies thousands of miles away in Latin America.

And the United Nations human rights committee blasted Iran for "serious, ongoing and recurring" human rights violations, in a non-binding resolution adopted on Friday.