The head of Israel's opposition Labor Party laid out a series of tough demands Sunday for joining the government, suggesting that Prime Minister Ariel Sharon (search) could face an uphill battle in shoring up his fractured coalition.

Opposition leader Shimon Peres said in an interview with The Associated Press that Sharon must agree to a far-reaching Israeli withdrawal from the West Bank and commit to negotiating with the Palestinians about the Gaza withdrawal.

Sharon has resisted similar ideas in the past, but may need Labor to shore up his fractured government. He has been widely expected to court Labor since two hard-line ministers resigned two weeks ago to protest the Gaza pullout plan.

The defections left the government with 59 seats in the 120-member parliament, threatening its ability to survive.

Labor, which holds 21 seats, has provided a "safety net" to Sharon, blocking no-confidence motions to bring down the government.

Neither Labor nor Sharon's Likud Party (search) have publicly committed themselves to a national unity government, and some lawmakers in both parties have expressed opposition to an alliance.

Peres laid down a series of strict conditions. He said Sharon must accept a wide ranging withdrawal from the West Bank, which Israel conquered in the 1967 Middle East War.

"My vision ... is for a return to the 1967 borders with minor adjustments for security and Jewish settlements," Peres told AP. He did not elaborate.

Sharon's plan calls for a withdrawal from only four isolated enclaves in the West Bank.

Sharon has not revealed how much West Bank land he might be willing to forgo in the future. But he has said that in exchange for the Gaza pullback, he wants to keep and expand several large settlement blocs in the West Bank — a demand that has won tacit support from President Bush.

Some 230,000 Israeli settlers live amid more than two million Palestinians in the Rhode Island-sized area. Palestinians demand a full withdrawal from all of Gaza and the West Bank.

Peres also said Sharon must change the nature of his Gaza withdrawal plan by negotiating directly with Palestinian officials.

"We can and should talk to Abu Ala," he said, referring to Palestinian Prime Minister Ahmed Qureia.

Sharon envisions a pullout coordinated with Egypt, which borders Gaza, and the United States, but without input from the Palestinian leadership. After nearly four years of fighting, he says the Palestinians are not serious negotiating partners.

Israel is also been seeking to reach out to Arab countries in an attempt to harness the momentum of its decision to withdraw from the Gaza.

"There is an attempt to reach the entire Arab world, including those that have no diplomatic ties with Israel, such as Libya and Sudan," said Ron Prosor, deputy director general of Israel's Foreign Ministry.

Libya has historically been one of Israel's most intractable enemies, while Sudan is widely regarded in Israel as a supporter of anti-Israel militant groups.

A senior government official said it was too early to respond to Peres' conditions for Labor-Likud unity.

"There have been no negotiations, no invitations," the official said on condition of anonymity. "When an invitation comes I'm sure there will be negotiations on the conditions for cooperation."

In other developments, several hundred Palestinian protesters clashed with Israeli soldiers and border police Sunday in the West Bank village of Azawiyah. Residents have held a series of demonstrations in recent days against construction of a separation barrier that Israel is building in the West Bank.

Palestinians say Israel plans on confiscating thousands of acres of land in the area to build the structure, which Israel says is needed to protect against suicide bombings. Palestinians criticize the barrier as a land grab.

In Sunday's violence, an elderly Palestinian man approached the troops and was thrown to the ground, witnesses said. Troops used tear gas and clubs to disperse the crowd, but no serious injuries were reported.

The army said the soldiers had fired tear gas after the crowd started to throw stones.

Also on Sunday, Palestinian laborers crossed into Israel from the Gaza Strip for the first time since Israel barred workers from entering the country after the killing of Hamas leader Sheik Ahmed Yassin three months ago.

Israel opened the Erez border crossing on Thursday to 500 laborers, the army said, but none showed up. Early Sunday, the hundreds of workers crossed into Israel.

Before Israel's killing of Yassin, up to 15,000 Palestinian laborers crossed daily into Israel. The travel ban was a further blow to the poverty-ridden Gaza Strip, which reportedly has a 60 percent unemployment rate.