World oil prices rallied slightly above 60 dollars a barrel Thursday, amid worries about the security of supplies in Nigeria and Iran.

New York's main contract, light sweet crude for delivery in April, went up 45 cents to close at 60.47 dollars a barrel.

In London, the price of Brent North Sea crude for April delivery gained 1.03 dollars to 61.06 dollars a barrel.

U.S. Defense Secretary Donald Rumsfeld warned Thursday that the U.S. military will take " appropriate" action to stop "Iranian forces infiltrating Iraq".

Traders are still concerned about the possibilities that Iran's oil exports would halt if the United Nations imposes Teheran an international sanction for its nuclear activities. Iran is OPEC's number-two producer behind Saudi Arabia, making four million bpd of oil and exporting 2.4 million bpd.

Nigerian separatist guerrillas, who are holding three Western oil workers hostage, shot dead five government soldiers in a firefight in the Niger Delta, a military spokesman said Thursday.

In Nigeria, some 455,000 bpd of its oil production- about one- fifth of the country's daily output,or less than 1 percent of total global demand, is still shut after a series of militant attacks. Nigeria is Africa's leading oil producer and the fifth- biggest source of U.S. oil imports.

U.S. Department of Energy announced Wednesday that its crude oil inventories rose by 6.8 million barrels to 335.1 million in the week to March 3, 10 percent higher than at the same stage one year ago, and are at their highest level since May 1999.

The Organization of Petroleum Exporting Countries (OPEC), who pumps about a third of the world's oil, reassured on Wednesday that there will be no change to the group's 28 million barrels per day ceiling that has been in place since July 2005, despite forecasts for lower demand in spring.