Crawford, Texas ? President Bush and Israeli Prime Minister Ariel Sharon differed strongly and publicly Monday over the future of West Bank settlements under the U.S.- backed peace plan, underscoring the fragile nature of negotiations to end the decades-long conflict between Israel and the Palestinians.

Palestinian workers pour concrete into the structure of a new building at an Israeli settlement in the West Bank. President Bush urged Israeli Prime Minister Ariel Sharon to halt settlement expansion.

Bush condemned the expansion of Jewish settlements as a violation of the so-called “road map” plan for a two-state solution. But Sharon, who has proposed expanding a major settlement east of Jerusalem, said Monday that the development and others would be protected under any final agreement and remain part of Israel. Their comments came after the two leaders met for an hour and a half.

“I told the prime minister of my concern that Israel not undertake any activity that contravenes road map obligations, or prejudice final status negotiations,” Bush said.

The impasse demonstrated that Bush and Sharon, despite a close alliance over the past four years, now offer widely different interpretations of what the U.S.-supported peace plan means for settlements.

Sharon refused Monday to concur with Bush’s statement that the expansion violates the road map. Instead, the prime minister insisted that West Bank settlements will be protected.

“It is the Israeli position that the major Israeli population centers will remain in Israel’s hands under any future final status agreement with all related consequences,” he said.

President Bush and Israel's Prime Minister Ariel Sharon, left, walk through a bed of bluebonnets, the state flower of Texas, as they arrive for a joint news conference Monday in Crawford, Texas.