The water level in the Dead Sea, an ancient salt lake whose shores are the lowest dry places on the earth’s surface, has been dropping by more than three feet a year, mainly because most of the water in the Jordan River, its main feeder, has been diverted by Israel, Jordan or Syria for domestic use and irrigation; very little now reaches the lake. Potash industries on either side of the lake have also had a detrimental impact. About 25 miles of the Dead Sea’s shoreline lie in the Israeli-occupied West Bank and are claimed by the Palestinians as part of a future state.

Israeli officials said that proposals would soon be solicited internationally from private companies to build and operate a desalination plant in Aqaba, which is meant to operate on a commercial basis, selling the potable water to Jordan and Israel. A brine pipeline to the Dead Sea, estimated to cost at least $240 million, would be financed by donor countries and organizations, with the World Bank providing a bridge loan.

The brine pipeline will run through Jordanian territory, because the planning process in Jordan is quicker and less liable to be slowed by the objections of environmentalists and other opponents, according to Israeli officials. They said that the added brine’s effects on the Dead Sea would be carefully monitored.

The project has been discussed and studied in various forms for 20 years. Speaking on Israeli Army Radio on Monday, Silvan Shalom, the Israeli cabinet minister responsible for water projects and for regional cooperation, called the agreement “historic.” But critics said it was far less ambitious than an earlier proposal for a canal that would also exploit the altitude difference between the Red and Dead Seas to generate hydroelectricity.

Regional tensions also manifested themselves. Shaddad Attili, the head of the Palestinian Water Authority, said the agreement was essentially one between Israel and Jordan, with the Palestinian Authority involved because it shares part of the Dead Sea coastline. “We gave our support to Jordan,” he said.