US President George W Bush on Friday signed up to new legislation that tries to curb the illegal trade in "blood" diamonds.
Americans buy billions of dollars worth of diamonds each year
Such stones, also known as conflict diamonds, are thought to have financed violent civil conflicts in African countries including Angola, Sierra Leone and DR Congo.
"Conflict diamonds have been used by rebel groups in Africa to finance their atrocities committed on civilian populations and their insurrections against internationally recognised governments," Mr Bush said.
The new law provides the means for the United States to implement the Kimberley Process, a certification scheme which went into effect in January and aims to track each diamond from mine to shop window.
The trade in blood diamonds is thought to comprise about 3% of the annual global diamond trade, said to be worth about $7bn.
More than 50 diamond importing and exporting countries have signed up to the scheme, but the participation of the US is crucial as Americans buy two-thirds of the world's supply.
The Clean Diamond Trade Act requires all batches of diamonds to be accompanied by a special hard-to-forge document produced by national authorities to certify the country of origin.
Campaigners say diamond sales in Africa have funded civil war
Within the US, dealers are required to maintain records of all shipments for inspection.
The Kimberly Process has the backing of diamond industry representatives and human rights groups as well as governments.
However, some rights groups have expressed concerns that the process lacks proper oversight of national registration schemes.
Participant nations are scheduled to meet next week in Johannesburg, South Africa.