A growing number of oil companies, trading houses and other international companies have stopped doing business with Iran this year amid a U.S. drive to isolate Tehran and international efforts to impose tougher sanctions.

Here are some of the companies:

• Italy's oil and gas major Eni is handing over operatorship of Darkhovin oilfield in Iran to local partners to avoid U.S. sanctions, Eni told U.S. authorities on April 29. Eni, present in Iran since 1957, said it had only residual activities relating to buy-back contracts dating to 2000 and 2001.

• French energy giant Total will cease gasoline sales to Iran if the U.S. passes legislation to penalize fuel suppliers to Iran, its chief executive said on April 26.

• Russian oil major Lukoil will cease gasoline sales to Iran, industry sources said on April 7, following a similar decision by Royal Dutch Shell in March. Lukoil had supplied some 250,000 to 500,000 barrels of gasoline to Iran every other month, traders said.

• Malaysia's Petronas has stopped supplying gasoline to Iran, a company spokesman said on April 15. Petronas last shipped a gasoline cargo into the Iranian port of Bandar Abbas on March 4 or 5, industry sources said.

• Luxury carmaker Daimler announced plans on April 14 to sell its 30% stake in an Iranian engine maker and freeze the planned export to Iran of cars and trucks. The announcement followed similar action by German insurers Munich Re and Allianz.

• India's largest private refiner, Reliance Industries, will not renew a contract to import crude oil from Iran for financial year 2010, two sources familiar with the supply deal said on April 1.

• Oil trading firms Trafigura and Vitol are stopping gasoline sales to Iran, industry sources said on March 8.

• Ingersoll-Rand, a maker of air compressors and cooling systems for buildings and transport, said it will no longer allow subsidiaries to sell parts or products to Tehran.

• Oilfield services company Smith International said on March 1 it was actively pursuing the termination of all its activities in Iran.

• Caterpillar, the world's largest maker of construction and mining equipment, said on March 1 it had tightened its policy on not doing business with Iran to prevent foreign subsidiaries from selling equipment to independent dealers who resell it to Tehran.

• German engineering conglomerate Siemens said in January it would not accept further orders from Iran.

• Glencore ceased gasoline supply to Iran in November 2009, according to traders. The Swiss-based commodities trader in January declined comment on the matter.

• Chemical manufacturer Huntsman announced in January that its indirect foreign subsidiaries would stop selling products to third parties in Iran.

• Accounting giants KPMG, PricewaterhouseCoopers, and Ernst & Young have declared themselves free of any business ties to Iran.

Still Dealing With Iran

The website of New York-based lobby group United Against Nuclear Iran lists scores of companies it says still do, or have done, business with Iran. The list includes companies that have severed links with Iran.

The U.S. Government Accountability Office reported in April that 41 foreign companies were involved in Iran's oil, natural gas and petrochemical sectors from 2005 to 2009. In a new report, the GAO said seven of those companies received U.S. government contracts worth nearly $880 million. These were:

Repsol of Spain; Total; Daelim Industrial Company of South Korea; Eni; PTT Exploration and Production of Thailand; Hyundai Heavy Industries of South Korea; and GS Engineering and Construction of South Korea.

Russia's Gazprom confirmed in March it was in talks with Iran on developing the Azar oil field.