Washington - US President George W Bush designated three areas of the Pacific Ocean as national monuments on Tuesday, preserving vast areas of waters rich in sea life for scientific research.

The three new monuments in remote areas of the Pacific near the US territories of American Samoa and Wake Island consist of a combined 518,000 square kilometres - slightly larger than Spain.

Bush made the designations under the Antiquities Act of 1906 that allows presidents to set aside places of historic, cultural or scientific significance.

"I am using that authority to designate three beautiful and biologically diverse areas of the Pacific Ocean as new marine national monuments," Bush said, as he prepares to leave office in two weeks.

Presidents often use their final days in office to issue executive orders or regulations, some of them controversial. Bush reversed many of predecessor Bill Clinton's proclamations after taking office.

The three areas designated by Bush will be free from oil or natural gas exploration and fishing. (dpa)