RAMALLAH (AFP) - Palestinian negotiators said on Thursday that Israeli Prime Minister Ehud Olmert's resignation would deal a swingeing blow to peace hopes at a crucial time in the negotiations. While the Islamist Hamas hailed the news, Palestinian negotiators mourned the loss of a man they felt is "serious" about peace. The Palestinian Authority's official position is that the corruption allegations that have dogged Olmert and Wednesday's surprise news he will step down after September's contest for the leadership of his Kadima party are an internal matter. Palestinian President Mahmoud Abbas said on Thursday he would work with whoever becomes premier. But privately many Palestinian officials feel they will lose a partner who was willing to negotiate over the most contentious issues of Jerusalem and borders, which have blocked previous peace efforts. "We have taken part in the most important negotiations (with Olmert) since 1991," said one senior negotiator under condition of anonymity. "The Israelis listened to us and discussed the issues," he added. Another top Palestinian negotiator and former minister, Mohammed Ashtiyah, said Olmert was "serious and involved" in the peace talks, even though they have so far failed to make major progress. "The negotiations have reached a crossroads. We do not know who will make up the next government coalition, or the name of the future prime minister," Ashtiyah said. Israeli Foreign Minister Tzipi Livni and Transport Minister Shaul Mofaz are the two front-runners in the race to take over the leadership of the centrist Kadima. "If Livni is elected, the negotiations can continue. But if Mofaz wins, that will be more difficult," Palestinian political economist Hani al-Masri said. Meanwhile, the United States, Israel and the Palestinians agreed in talks Wednesday to strive for a Middle East peace deal without any "shortcuts", Palestinian negotiator Saeb Erekat said. The parties also regarded Israeli Prime Minister Ehud Olmert's announced resignation Wednesday as an internal matter that would not dampen negotiations for an Israeli-Palestinian agreement, officials said. "We will not opt for an option of partial agreements, shortcuts or anything short of a full agreement on all issues," Erekat told reporters after he and chief Palestinian negotiator Ahmed Qorei held talks with US Secretary of State Condoleezza Rice and Israeli Foreign Minister Tzipi Livni. Rice, who has criss-crossed the Middle East since then to forge the deal, described the talks Wednesday as "very fruitful." She acknowledged that issues hampering a resolution to the six-decade conflict "are difficult and they've always been difficult. "There's nothing surprising in that." The chief US diplomat said the objective to fulfil the Annapolis goals "remains the same," moving to allay any fears that a deal reached would not be comprehensive. Rice also gave a reassurance that Olmert's decision to quit in the face of corruption probes would not affect the talks.