Meanwhile, oil minister said on Saturday the Islamic Republic's Caspian Sea oil acreage might be opened to foreign investment through highly sought after production sharing deals instead of its more restrictive buy-back contracts.

"Production sharing contracts (in the Caspian) are possible -- everything is possible once it has been studied," Bijan Zanganeh told reporters on the sidelines of the second ministerial meeting of the Gas Exporting Countries Forum (GECF) in Algiers.

"The Caspian is a new area for us -- we have not done anything like that."

International oil companies have already invested some 12 billion dollars to develop oil and gas field on shore and in the gulf using buy-back contracts.

Under buy-back deals a foreign firm recoups its capital expenditure and makes a profit by receiving a cash payment from part of the project's output.

The Iranian oil minister said his country could not afford to wait for the demarcation of the heartily-disputed Caspian Sea before getting back to work.

The Caspian has yet to be legally apportioned to the countries surrounding it -- Russia, Kazakhstan, Iran, Turkmenistan and Azerbijan.