Iran has warned its Gulf neighbours to not make up for any shortfall in its oil exports under new Western sanctions, its OPEC representative said in comments published on Sunday.

"We would not consider these actions to be friendly," Mohammad Ali Khatibi was quoted as saying by the Sharq newspaper.

"If the oil producing nations on the Persian Gulf decide to substitute Iran's oil, then they will be held responsible for what happens," he said.

Khatibi said Iran would consider any Gulf member of the Organisation of Petroleum Exporting Countries that "cooperate with the adventurous (Western) nations in substituting Iranian oil to be accomplices."

If they did so, "one cannot predict the consequences," he was quoted as saying.

Khatibi added that, if the Gulf nations do not cooperate with the West by pumping more oil, "then its 90 percent probable that nothing would occur."

The warning comes as the United States and the European Union step up sanctions to curb Iran's oil exports and revenue.

Iran is the second-biggest oil exporter in OPEC after Saudi Arabia, with output of some 2.5 million barrels per day. It depends on petroleum revenues for more than half its state income, earning around $75 billion annually from the exports.

Saudi Arabia has reportedly told a senior US lawmaker it stands ready to increase its current oil output of 10 million barrels per day should new sanctions curb Iranian oil exports.

Saudi Arabia's oil minister, Ali al-Naimi, said in Sunday's edition of his country's al-Watan newspaper that "Saudi Arabia is able to produce 12.5 million barrels per day to meet the needs of the world market and satisfy any increase in demand from consumer countries."

French Foreign Minister Alain Juppe said last Tuesday that unnamed oil producing countries will boost their output to make up for a planned EU ban on Iranian oil expected to be announced January 23.

"Other countries are ready to increase production to avoid an effect on prices. We have made discreet contacts in this direction. The producers don't want to talk about it, but they are standing ready," he said.

China, Iran's biggest oil customer, has rejected new US sanctions that seek to block Iran's central bank from clearing oil payments.

However Chinese Premier Wen Jiabao was Sunday visiting his country's prime supplier, Saudi Arabia, as part of a Middle East tour of oil-producing nations.

He was also to visit the United Arab Emirates and Qatar.