The decision by Brussels is likely to play into the hands of BP Amoco which would dearly like full control of the joint venture.
It was widely expected that Exxon-Mobil would be forced to dispose of its share in the joint venture following last year's merger announcement.
The BP-Mobil joint venture has an estimated 11 per cent of the European petrol market. With Exxon, the two groupings would control 20 per cent of the market, giving rise to a situation where competition could be compromised.
EC officials are thought to have been concerned about the 80 per cent share of the German natural gas market that Exxon-Mobil would command if the deal were allowed to go through without disposals. The BP-Mobil joint venture, formed in 1996, operates 8,900 service stations and has 925,000 barrels a day of refining capacity. BP controls 70 per cent of the petrol-retailing part of the venture and Mobil has a 51 per cent share of its much smaller lubricants operations.
BP contributed $3.4bn of assets to the venture and Mobil put in $1.6bn, valuing the business at $5bn. The profitability of the joint venture has improved, increasing its value.
Although BP Amoco does not have any first right of refusal to buy out Mobil's stake, analysts question how many other bidders would be interested in paying $2bn for a business which was 70 per cent owned by BP Amoco.
But Mobil insiders insist it will not be forced to sell its stake on the cheap, indicating that there will be interest from other parties.