The Palestinian Authority has appealed to the world powers behind Middle-East peacemaking to stop Israel from extending its security barrier in the West Bank. Israel is risking more controversy by announcing plans to build new homes for Jewish settlers.

Palestinian chief negotiator Saeb Erekat says the Palestinian Authority sent out letters to the members of the so-called "Quartet" on Middle East peace-making, the United States, Russia, the European Union and the United Nations.

The letters call for international intervention following the decision Wednesday of the Israeli Cabinet to approve a new phase of its security barrier in the West Bank.

Israel says the project is necessary to prevent Palestinians from crossing into the Jewish State to carry out terror attacks. Israel also plans to build separate barriers around some Jewish settlements.

Mr. Erekat says such moves are threatening, to "demolish" efforts by President Bush to promote the international road map to peace.

"The Israeli Government decision to continue building the wall and to add the settlement of Ariel to it is leading to the biggest failure of President Bush's two-state solution," he said. "It is undermining and sabotaging President Bush vision of a two-state solution, is undermining and sabotaging the peace process, undermining and sabotaging the 'road map'."

Mr. Erekat says that the project will cut Palestinians off not only from Israel but also from fellow Palestinians.

In a separate move, Israel announced it had approved the building of 550 new homes for Jewish settlers in the West Bank.

The decision has been condemned by the Israeli group, Peace Now, which opposes Jewish settlements.

The organization says that since the beginning of the year, Israel has approved tenders for the building of a total of 1,300 new homes in settlements, with a capacity for 5,000 new settlers.

The Palestinian leadership says such communities take away land on which they want to found a future independent state.

Senior officials of the U.S. administration have also warned that an expansion of Jewish settlements threatens to destroy efforts to end the Israeli-Palestinian conflict.