White House officials say Bush will elevate the area now known as the Northwestern Hawaiian Island Coral Reef Ecosystem Reserve to national-monument status. The designation will immediately afford the region the strongest legal protections, with fishing and commercial operations immediately outlawed and visitors primarily limited to scientific researchers.

"It's the ocean equivalent of Yellowstone, Yosemite and the Grand Canyon all rolled into one," says Joshua Reichert, director of the environmental program of the Pew Charitable Trusts in Philadelphia.

The area comprises 140,000 square miles of ocean dotted with dozens of coral reefs and tiny islands; it is a 1,400-mile-long, 100-mile-wide swath of pristine marine habitat larger than all U.S. national parks combined.

The area is considered an ecological jewel. It is a nesting and breeding site to more than 14 million seabirds and home to 7,000 marine and terrestrial species, more than a quarter of which are found nowhere else in the world.

It is an important nesting area for the threatened Hawaiian green sea turtle and home to the endangered Hawaiian monk seal, of which only 1,300 remain. The coral reefs of the region provide vital breeding and nursery habitat for numerous fish and other marine species.

The president can create a national monument under the special authority of the Antiquities Act, which allows the White House to set aside an area of particular national importance for protection, conservation or preservation, said James Connaughton, a senior environmental adviser to the president.

There are 13 national marine sanctuaries in U.S. waters, and White House officials say this new one will be seven times larger than all of them combined. It is almost 100 years in the making, with U.S. presidents setting it apart with increasing levels of protection.

In 1909, President Theodore Roosevelt designated the area a refuge to stop the slaughter of seabirds by Japanese poachers who took the feathers for use in ladies' hats.

In the 1990s, overfishing caused the collapse of the lobster population, leading to the deaths of many monk seal pups that depend upon the crustaceans for food. In 2000, President Clinton increased the protections by issuing an executive order.

Bush had been expected to turn the reserve into a marine sanctuary, a process that had been underway for the past five years.

But after talking to federal and state officials and native Hawaiian leaders, the White House decided there was sufficient consensus to instead grant the region immediate monument status.

The sanctuary will be overseen by the National Oceanic and Atmospheric Administration.

 The area is home to numerous ancient Hawaiian religious and archeological sites.