By Peter N. Spotts | Staff writer of The Christian Science Monitor

Imagine President Bush, Britain's Tony Blair, and Junichiro Koizumi of Japan forming an alliance and "signing" their pact with a few quick, solemn passes of a soccer ball on the White House lawn.

A team of archaeologists from the United States and Guatemala says it has uncovered a Mayan altar stone whose intricate carvings record a treaty and a similarly sporty signing ceremony.

Unearthed at the site of the ancient city-state Cancuén in Guatemala, the find is one of two newly discovered monuments that researchers say are revealing the extent of Cancuén's power and reach at a critical time in Mayan history. They add to a growing body of evidence that suggests the Central American civilization fell, not because of environmental factors, as some experts believe, but for a complex set of economic and political reasons.

"It's like the fall of Rome," says Arthur Demarest, a Vanderbilt University archaeologist and one of two scientists heading the project.

The monuments offer some of the freshest evidence for uneven socioeconomic decline: Just as much of the Mayan empire was crumbling, Cancuén was on the rise.

For example, the altar stone there depicts one of the ceremonial games in which a lesser lord seals his alliance to Taj Chan Ahk, who ruled Cancuén during much of the last half of the 8th century AD. It's the Mayan equivalent of a modern-day "photo op," says Dr. Demarest.

The second monument is an intricately carved stone panel from a ceremonial ball court within the king's sprawling palace. It clearly places Taj Chan Ahk on the thrones of other major centers nearby as he installs or promotes local officials. It declares him "holy King of Cancuén; holy King of Machaquila," a kingdom some 25 miles to the north.

Two altar stones found earlier - one by looters and recovered last year by Guatemalan authorities - hinted at this broader reach. But the inscriptions were not as well preserved. The third altar stone and the wall panel appear to clinch it. Essentially, the panel proclaims: "Hey, man, I'm king of the whole region," says Demarest. Thus, a city that some researchers had held to be merely a vassal to a distant kingdom is emerging as having been a power center in its own right.

Taj Chan Ahk "controlled the Mayan equivalent of the Mississippi River" from his spot on the Pasión River as it finishes its tumble out of volcanic highlands to the south, Demarest says during a phone interview from Cancuén.

Taj Chan Ahk controlled the trade in jade, pyrite, obsidian, feathers, and other highly prized commodities. He therefore was able to remain largely independent of bigger, more militaristic city-states through economic clout and shrewd alliances, even as war and decline elsewhere were bringing the civilization's "classic" period to a close.

Taken in a broader context of excavations elsewhere, the story of the Mayan civilization's demise is growing increasingly complex. Some researchers have favored climate change as an explanation for the Mayans' downfall. Yet the archaeological record suggests a more gradual, uneven decline that predates changes in climate and mirrors that of other civilizations.

The monuments are noteworthy as much for their beauty as they are for the history they reveal, says Frederic Fahsen, an expert in Mayan hieroglyphics and the project's chief translator.

"This is one of the greatest masterpieces of Mayan art ever discovered in Guatemala," he says of the stone panel. "The images of the rulers and the historical text are deeply and finely carved in high relief and miraculously preserved."

The extraordinary level of preservation stems from the fact that when the portion of the wall containing the panel collapsed, it fell face down into the muck, Demarest says. "It has these little, fine glyphs that look like they were made yesterday."

Even as the international team is combing Cancuén to fill in gaps in its history, the team has located another city nearby.

"We found this big site two weeks ago" located at another key spot along the Pasión River, Demarest says. "We haven't even excavated there yet, but it could be an early classic center."