President Bush is to create the world's largest marine protection area in a huge swath of the Pacific Ocean.
Mining and commercial fishing will be banned in an area measuring 195,000 square miles which includes the Mariana Trench, the deepest ocean trench on the planet. Rose Atoll in American Samoa and seven islands strung along the equator in the central Pacific will also come under the protection plan.
The atolls, reefs and underwater mountains of the designated area are the habitat of hundreds of unique species of birds and fish including the world's largest land crab and the rare Malaysian megapode, a bird that incubates its eggs in the heat of underwater volcanoes.
It also harbours some of the rarest geological formations on earth; the Mariana Trench lies 36,000 feet below sea level - 6.8 miles deep. Its deepest point is deeper than Mt Everest is tall, and it is five times the size of the Grand Canyon.
Rose Atoll, the smallest atoll in the world with only about 20 acres of land, is home to giant 85ft tall trees and is a vital nesting ground for threatened green sea turtles and endangered hawksbill sea turtles.
"These locations are truly among the last pristine areas in the marine environment on Earth," said James Connaughton, chairman of the White House Council on Environmental Quality, announcing the plans which will be made official by Mr Bush at a White House ceremony today.
The protected areas will extend 50 nautical miles off the coral reefs and atolls at the three monuments, which will be officially called the Marianas Marine National Monument, Rose Atoll Marine National Monument, and the Pacific Islands Marine National Monument.
Environmental groups welcomed the move, although they said they had hoped the protection zone would extend for 200 nautical miles, the full extent of the US exclusive economic zone.
"We and others in the environmental community have been at odds with this administration on lots of things, but if one looks at this one event it is a significant conservation event," said Joshua Reichert, managing director of the Pew Environment Group, which lobbied for the monuments' designation.
"In a more symbolic level, it sends a message that we have finally arrived at a point where we are beginning to think about the sea in the same way we have thought about the land -- that there are special places under threat that need to be protected," he said.
It will be up to President-elect Barack Obama to hammer out how the areas will be managed, and to make sure the prohibitions are enforced.
The protection of the Mariana Trench will give a boost to Mr Bush's environmental credentials, long battered by criticism that he has not done enough to combat air pollution or global warming.
However two years ago he made a huge swath of the Northwestern Hawaiian Islands a national monument, barring fishing, oil and gas extraction and tourism from its waters and coral reefs.