Venezuelan President Hugo Chavez was given a warm welcome by his Iranian counterpart Mahmoud Ahmadinejad in Tehran on Monday.

Chavez is making a one-day visit to Iran to further boost ties with a close ally in what is his fourth trip to the country in the last two years, the official Islamic Republic News Agency reported.

On Sunday, an Iranian foreign ministry spokesman said Chavez and Ahmadinejad would sign various economic deals including an agreement on small and medium enterprises.

Chavez flew in from Saudi Arabia where he and Ahmadinejad attended the weekend's OPEC (Organisation of Petroleum Exporting Countries) summit in Riyadh.

During the gathering, the two firebrand leaders echoed one another's stance, blaming US President George W. Bush's policies for the decline of the (US) dollar and its negative effect on other countries, and challenging Saudi Arabia's reluctance to mention weak dollar concerns in the summit's final declaration.

Ahmadinejad claimed OPEC's member countries want to convert their cash reserves into a currency other than the depreciating US dollar, which he called a "worthless piece of paper."

Chavez said the dollar was in free-fall and that its "empire" must end, and proposed trading oil in a basket of currencies excluding the dollar.

But the two were unable to generate support from enough in the 13-member cartel - many of whom, including Saudi Arabia, are staunch US allies.

Ties between Iran and Venezuela have been growing stronger, with both leaders strongly condemning US policies.

Chavez has defended Iran's disputed nuclear programme, dismissing Washington's concerns that Tehran is secretly trying to develop atomic weapons.

Chavez warned the US on Saturday that oil prices could more than double if Washington attacked his country or Iran - part of a provocative opening address at the OPEC summit.