"White phosphorus is a conventional munition. It is not a chemical weapon. They are not outlawed or illegal," Lieutenant-Colonel Barry Venable, a Pentagon spokesman, told the BBC in an interview.

"We use them primarily as obscurants, for smokescreens or target marking in some cases. However, it is an incendiary weapon and may be used against enemy combatants."

Italy's state television RAI claimed last week the highly flammable munitions were used against insurgents and civilians in the Iraqi town of Fallujah in November last year.

Radical left-wing Italian politicians joined a protest at the US embassy on Monday, including communist deputy Piero Folena, who called for a United Nations inquiry into the alleged use of such weapons in Fallujah.

The RAI documentary, "Fallujah -- The Hidden Massacre", said the US military used a kind of napalm and white phosphorus in the battle, a claim denied by the US State Department.

Robert Tuttle, US ambassador to Britain, wrote in a letter published by The Independent newspaper on Tuesday that "US forces do not use napalm or white phosphorus as weapons".

But Venable said white phosphorous was useful to shift insurgents from positions that could not be targeted by normal artillery.

"It was used as an incendiary weapon against enemy combatants," he told the

"When you have enemy forces that are in covered positions that your high explosive artillery rounds are not having an impact on... one technique is to fire a white phosphorus round into the position," he said.

"The combined effects of the fire and smoke -- and in some case the terror brought about by the explosion on the ground -- will drive them out of the holes so that you can kill them with high explosives."

All rights reserved. © 2005 Agence France-Presse. Sections of the information displayed on this page (dispatches, photographs, logos) are protected by intellectual property rights owned by Agence France-Presse. As a consequence, you may not copy, reproduce, modify, transmit, publish, display or in any way commercially exploit any of the content of this section without the prior written consent of Agence France-Presse.