The deal is thought to potentially be worth about $100 billion.

The Wall Street Journal reported Friday that the two sides are trying to conclude the deal in coming weeks before potential sanctions are imposed on Iran for its nuclear ambitions.

In exchange for China Petrochemical Corp. developing Yadavaran, one of Iran's largest oil fields, China would agree to buy 10 million tons of liquefied natural gas a year for 25 years beginning in 2009, Asian magazine Caijing said, citing China Petroleum Corp. board member Mou Shuling.

China Petroleum, also known as Sinopec, is Asia's largest refiner.

Chinese and Iranian officials in Beijing said they could not confirm the report.

Beijing has strongly urged that a diplomatic solution be found to the impasse over Iran's nuclear program.

Western nations say Iran plans to develop nuclear weapons, but Iran says it wants only to generate electricity.

Growing international concern about its aims contributed to Tehran being reported to the U.N. Security Council by the 35-nation board of the International Atomic Energy Agency, the U.N.'s nuclear watchdog.

Next month, the Security Council is to consider Iran's nuclear activities. The council can impose economic and political sanctions on Iran, but members China and Russia could veto such measures.