By Mark Doyle BBC world affairs correspondent

The Kimberley Process aims at cracking down on the multi-billion dollar trade in the gemstones which have been mined in war zones.

The diamond trade has financed conflict in Angola, among other countries

The plan - named after a diamond-mining town in South Africa - aims to stop the diamond industry fuelling bloodshed in wars like that in the Democratic Republic of Congo.

But the lure of diamonds, for the unscrupulous, as an ideal repository of illicit wealth means the plan will undoubtedly encounter resistance.

Small proportion

Diamonds are a warlord's best friend.

Although conflict gems represent only a small proportion - less than 5% - of all diamonds, it is no coincidence that wars have raged in diamond producing areas of Sierra Leone, Angola and Congo.

Diamond mines themselves are fought over, but the gems also fuel conflict because they are a high-value, easily hidden commodity favoured by arms dealers, smugglers and criminals of all types.

It's in the interests of producing countries to have a scheme which says that the diamond is... above board Matthew Lockwood Action Aid

The Kimberley scheme for certifying diamonds as "conflict-free" has been agreed to by the main producing and consuming countries.

The stones will be exported with a certificate saying they are conflict-free, issued by producing-country governments.

The scheme is backed by development charities.

Smuggling concerns

Matthew Lockwood of Action Aid said: "The point to make about the scheme is that it will improve the situation for producing countries.

"It's in the interests of producing countries to have a scheme which says that the diamond is modern, it's properly audited, and it's above board.

"At the moment, not being able to say even how many diamonds are produced, let alone their sources, isn't in the interests of either the industry or the countries."

But charities add that the scheme as currently envisaged is flawed because there will be no independent monitoring of the conflict-free certificates.

They say that without tough independent monitoring to police the new laws, certificates could fall into the wrong hands, and smuggling will continue.