NEW YORK (Reuters) - The American Museum of Natural History sued an American Indian group Monday to block its claim to the 15.5-ton Willamette Meteorite, one of the museum's oldest treasures and a centerpiece of its newly opened planetarium.

The metallic iron meteorite, which is believed to have fallen to Earth 10,000 years ago from the Asteroid belt between Mars and Jupiter, holds a place of honor on the main floor in the planetarium's astrophysics hall. It has been viewed by countless scientists, teachers and schoolchildren for nearly a century.

The lawsuit alleged that the meteorite's ownership history dates back to at least 1855 when various Indian tribes voluntarily ceded the meteorite, which was once located in the upper Willamette Valley in Oregon, to the United States in exchange for reservation land and other considerations.

In 1905, the Supreme Court of the State of Oregon ruled that the meteorite belonged to the Oregon Iron and Steel Company as owner of the land on which the object was found. The company sold the meteorite to the American Museum of Natural History the next year for $20,600.

Almost immediately after its purchase, the museum began to study the object and it has been on almost continuous display since 1906.

According to the lawsuit, the current ownership dispute began during the fall of 1999 when representatives of the Confederated Tribes of the Grand Ronde Community of Oregon visited the museum. The federally recognized group consists of a number of tribes from the Upper Willamette Valley, including the Clackamas which ceded the meteorite in 1855, the suit said.

At the end of their visit, the representatives submitted a written claim for repatriation to the museum stating that the meteorite is a sacred object. It filed its claim under the federal law known at the Native American Graves Protection and Repatriation Act, known as NAGPRA. The law was written for the preservation and repatriation of Native American cultural and religious artifacts.

To obtain repatriation of a sacred object, a tribe must show that it is a sacred object, that the tribe owned or controlled it and that the museum does not have a right of possession, the suit said.

The museum alleged that the Oregon Indian group did not meet these requirements.