And the two states abutting its shrinking shoreline, Israel and Jordan, face formidable economic and ecological challenges in pondering how to save a unique natural wonder of the world.

They have begun to consider a "Red-Dead" solution - a canal to pump water from the Red Sea to the Dead Sea. But huge costs, and the risk both of damaging the Red's famed coral reefs and diluting the Dead's medicinal minerals, stand in the way.

Known as the Dead Sea because nothing can live in it, the world's saltiest body of water has fallen from 1,280 feet to 1,368 feet below sea level in the last 50 years.

The drop has accelerated to three feet a year recently, erasing a third of its ancient 366-square-mile size.

Modern economics are to blame - diversions to rain-starved farmland of Jordan River waters that feed the Dead Sea, and evaporation hastened by potash-mining in its southern basin.

Hotels and health spas built along the beach below spectacular rose- and orange-hued desert cliffs, as well as sites holy to Jews, Christians and Muslims, are now stranded a mile or more from the water's edge.

Retired Swiss couple Jean and Esther Haensenberger have been spending their annual "Kur" - a Central European tradition of taking medicinal baths to treat skin ailments and stress - at Israel's flagship Dead Sea resort of Ein Gedi since the 1980s.

At first, they could walk a few paces from the Ein Gedi Spa complex to the beach for a float in windless waters so buoyant that one can read a book while lying on one's back.

Now visitors board a tractor-drawn trolley that shuttles them half a mile to the water, avoiding a trudge across mudflats in sauna-like heat typifying the inland sea's micro-climate.

'RATHER SAD'

"It's over twice the distance out today. It's sad that another rare preserve of nature is vanishing," said Jean Haensenberger as he and his wife rode to the shore. "If the sea keeps going down, will people like us keep coming?"

The number of foreign tourists in Israel has dropped because of a 3-year-old Palestinian revolt. And tourism in Jordan has suffered from war and postwar turmoil in nearby Iraq.

Now the Dead Sea's retreat is worsening the economic fallout of Palestinian violence along the western shore by spawning subsidence - more than 1,000 "sinkholes" up to 65 feet deep and 82 feet across.

Caused by a dissolution of salt strata in underground fresh water replacing departed salt water, sinkholes have swallowed up groves of date palms, shut down Ein Gedi's tourist campsite and a nearby army base and scuttled a 5,000-room hotel project nearby.

A camp staffer and a worker at Ein Gedi's nearby palm plantation were sucked into collapsing sinkholes and injured.

Sinkholes appearing on the Jordanian shore have forced the evacuation of more than 3,000 people. Hundreds of millions of dollars worth of hotel-spa complexes in the planning could be at risk.

"We fear that by 2050 there will be just a small spot of water that will be a disaster economically and ecologically, if nothing is done," said Zafer Alem, secretary general of the Jordan Valley Water Authority.

"We are raising the red flag to the international community to help us save what is really a world heritage site, belonging not just to Jordan and Israel," he told Reuters by telephone.

PIPELINE MAY NOT BE PANACEA

At the Earth Summit in Johannesburg a year ago, Israel and Jordan agreed to look into building a "Red-Dead" pipeline that would run 200 miles along their rugged desert border.

Dubbed the "Peace Conduit," the canal would be the biggest Israel-Jordanian joint venture since their 1994 peace treaty.

Israeli officials cite the importance of cooperation with former Arab enemies as one of the main reasons they favor the Red-Dead canal over an older "Med-Dead" proposal to take water from the Mediterranean Sea, which would not involve Jordan.