The ruling Fatah Party on Thursday rejected Hamas's offer to form a national coalition cabinet and decided to function as an opposition force in parliament.
The offer was made by senior Hamas leaders almost immediately after it became clear that the Islamic movement had scored a landslide victory in Wednesday's parliamentary election.
Earlier, the Palestinian Central Election Commission announced that Hamas had won a majority in the Palestinian Legislative Council, capturing 76 of 132 seats. Fatah, on the other hand, suffered a humiliating defeat by winning only 43 seats.
Hanna Nasser, head of the commission, said the results could change slightly but were based on a count of 95 percent of the votes.
In response to the victory, Acting Prime Minister Ehud Olmert declared during a security cabinet meeting Thursday night that any Palestinian Authority government that included Hamas would not be a partner for Israel.
The Prime Minister's Office issued a statement after the cabinet meeting that read, "Israel will not negotiate with a Palestinian government, even if only part of it is an armed terrorist organization calling for Israel's destruction, and in any case will continue to strenuously fight terrorism everywhere."
Palestinian Authority Chairman Mahmoud Abbas responded to the election results with a veiled warning to Hamas. "The Palestinian Authority is a signatory to several international agreements, and any government established in the future will be required to implement them," he said. "This is the only way to end the occupation and to gain the support of the international community."
Fatah leaders who held an emergency meeting in Ramallah said they would stay away from a Hamas-led cabinet and would devote their efforts to rebuilding their party.
"We won't join Hamas," said former Palestinian Authority minister Saeb Erekat. "We will be in the opposition and work toward rebuilding Fatah."
The commission was originally planning to announce the semi-official results in the morning, but for unknown reasons decided to delay the announcement until the evening.
The results of the election were in stark contrast to exit polls that were published by several Palestinian institutions late Wednesday night and which predicted a Fatah victory.
"The people who conducted these polls are inexperienced and unprofessional," said Jerusalem-based political analyst Zakariya al-Qaq. "They also made serious mistakes in the public opinion polls they conducted before the election. I believe they were then trying to affect the voters' decision by presenting a distorted picture."
Hamas leader Ismail Haniyeh, head of the Change and Reform List, said his movement wanted to start talks immediately with Fatah and other Palestinian factions over the shape of a new cabinet.
"We want to meet with President Mahmoud Abbas and Palestinian factions immediately to begin consultations over the shape of a political partnership," he told reporters in the Gaza Strip. "The Palestinian people voted for resistance, and Hamas will turn this victory to the service of the Palestinian people and the protection of the resistance."
Haniyeh said he did not expect Abbas to resign in the wake of Hamas's victory.
"Our relations with Abbas are based on mutual respect despite the differences between us," he said. "We're not in a confrontation with him."
Hamas's overall leader, Khaled Mashaal, called Abbas from Syria and told him his movement was ready for a political partnership.
As news of the results started to trickle in, Hamas leader Mahmoud Zahar was quick to reiterate his movement's conditioned commitment to the unofficial truce with Israel.
"If Israel is going to continue commitment to what is called quietness, then we will continue," he said. "But if not, then I think we will have no option but to protect our people and our land."
Asked if a Hamas-run cabinet would negotiate with Israel, Zahar said even prior to his movement's victory there had been no movement toward peace and, therefore, there was no point in holding a dialogue at this time.
"We have no peace process," he said. "We are not going to mislead our people to tell them we are waiting, meeting, for a peace process that is nothing."
Zahar promised a complete overhaul of public services and administration.
"We are going to change every aspect, as regards the economy, as regards industry, as regards agriculture, as regards social aid, as regards health, administration, education," he said.
Even before the semi-official results were announced, thousands of Hamas supporters took to the streets in the West Bank and Gaza to celebrate their movement's victory.
Approximately 3,000 Hamas supporters converged on the PLC building here and raised their green flag on the roof. When Fatah activists tried to remove the flag, Hamas demonstrators pelted them with stones. The crowd dispersed when PA policemen fired warning shots into the air.