A United Nations report has singled out the control of minerals, including the tantalum used in some capacitors, as the driving force behind the war in the Congo.

A five-member panel, established by Kofi Annan, UN secretary general, has called on the organisation's Security Council to declare an embargo on the export of minerals such as coltan (tantalum), diamond, copper, cobalt and gold from or to Uganda, Rwanda and Burundi.

Rebel forces which control large areas of the Congo are supported militarily and financially by these countries.

The report also urges member states to freeze the assets of companies if they "continued to participate in the illegal exploitation of the country's natural resources".

Tantalum capacitors are a key component in mobile phones. The sector's rapid growth has led to a worldwide tantalum shortage and prices have risen significantly, swelling the coffers of the Congo's warring factions who control much of the supply of the material.

In January 2000, a kilogram of tantalum cost $65. Last December, the price was $550, although that has fallen back to about $375 today.

Eighty percent of the world's tantalum reserves are thought to be in Africa and, in turn, 80% of those are in The Congo. As a result, the control of tantalum ore has become a key strategic factor in the war.

The UN report says that the private sector plays a "vital" role in the continuation of the war and that the war will continue while the various forces can profit from controlling mineral resources.

Much of the tantalum mined in the Congo is supplied to the world market by the Great Lakes Mining Company. The company's largest shareholder is the Congolese Rally for Democracy (RCD), one of the rebel groups supported by the Rwandan government. The RCD makes at least $1m a year from tantalum.

The Tantalum-Niobium International Study Centre (TIC), which represents tantalum producers, processors and consumers, has not formally responded to the US report.

But it has urged its members not to obtain tantalum from environmentally sensitive areas in the Congo where illegal mining is taking place.

Judith Wickens of the TIC said: "We take this issue very seriously and the TIC will be considering its position very carefully."