Jason Greenblatt, President Trump’s Middle East envoy, center, is flanked by Tzahi Hanegbi, Israel’s minister of regional cooperation, left, and Mazen Ghunaim, head of the Palestinian Water Authority, during a news conference on Thursday in Jerusalem. (Ronen Zvulun/Reuters)

President Trump’s Middle East envoy, Jason Green­blatt, on Thursday announced a water-sharing agreement between Israel and the Palestinians that will provide additional supply to the parched populations in the West Bank and the besieged Gaza Strip.

The deal is part of a larger, previously announced plan to draw salty water from the Red Sea to a huge desalination plant, which will then move fresh water via pipeline to Jordan, Israel and the Palestinians. The undrinkable brine will be used to help replenish and restore the Dead Sea, which is slowly disappearing.

Greenblatt’s mediation on the water deal was the first fruit of the Trump team’s effort to see if it can bring Israel and the Palestinians back to peace negotiations. The agreement to provide more water to the Palestinians, at a reduced rate, is also designed to build some trust between the antagonists.

Israel will begin to provide the extra water to the West Bank and Gaza Strip now. The supplies will eventually come from a desalination plant linked to a Red Sea-Dead Sea pipeline, to be completed in four or five years.

Greenblatt, who has been taking meetings with Israeli Prime Minister Benjamin Netanyahu and Palestinian Authority President Mahmoud Abbas, called the water deal “an important step forward.”

Trump’s envoy declined to answer any questions at the news conference here about how his effort to renew peace negotiations are going.

Mazin Ghunaim, head of the Palestinian Water Authority, said the increased supply of water “will reduce the suffering of the Palestinian people, which has been worsened by the beginning of summer and the crises that they are living through.”

About one-third of the additional supply will go to Gaza, “where more than 97 percent of the water is not drinkable,” he said.

Tzahi Hanegbi, Israel’s minister of regional cooperation, said that after years of stalemates, the Red Sea project will move forward. He thanked both Green­blatt and the Palestinians. He called the desalination and pipeline venture the “biggest, most ambitious project ever initiated in our area.”

“It will supply a significant amount of water to Jordan, to Israel and to the Palestinians. It will help us challenge the biggest problem the Dead Sea is facing — the evaporation of a meter a year — and it will also harness green energy,” Hanegbi said.