Haniyeh, the leader of the Islamist Hamas movement, told Reuters in an interview that his group would not oppose an Arab peace initiative which the summit is expected to relaunch, but would not give in on the Palestinian refugees' right of return.
"What concerns me more than anything else ... is not to compromise on the fundamental Palestinian rights, foremost being the right of return," Haniyeh said shortly before the summit opened.
"I expect the Arab summit meeting in Riyadh to reiterate the Arab countries' commitment not to compromise in any way on the Palestinian refugees right of return under any circumstances," Haniyeh said.
Arab leaders officially began the two-day summit in Saudi Arabia on Wednesday.
At the summit, United Nations Secretary-General Ban Ki-moon urged Arab leaders to prove they were serious about peace with Israel by reviving their five-year-old initiative.
"The Arab peace initiative is one of the pillars for the peace process .... This initiative sends a signal that the Arabs are serious about achieving peace," Ban told Arab leaders, according to an Arabic translation.
"When I was in Israel I urged my Israeli friends to take a new look at the initiative. Here in Riyadh, I also urge you, my Arab friends, to benefit from this initiative and reiterate your commitment to it because the situation is dangerous."
At the summit, Arab League chief Amr Moussa urged Israel to accept the initiative rather than ask for changes.
"The Israelis response was to ask for an amendment. We tell them to accept it first," Moussa told Arab leaders at a summit in Saudi Arabia.
"We are at a crossroads, it is either we move towards a real peace or see an escalation in the situation."
Hamas adopts ambiguity policy on Arab peace plan
In discussions with Haaretz Tuesday, a number of leading Hamas figures in the Gaza Strip said the group would refrain from expressing its views on the Arab peace initiative that members of the Arab League, including the Palestinian Authority, are expected to support during the summit in Riyadh.
The figures said the organization would adopt a policy of ambiguity on its stance vis-a-vis the peace initiative. However, senior Hamas officials admitted that they are opposed to parts of the initiative relating to a peace agreement with Israel or its recognition.
Palestinian sources said Tuesday that Hamas political bureau chief Khaled Meshal has promised Saudi Arabia's King Abdullah not to disrupt the decisions of the summit.
The same sources said that the policy of ambiguity stems from concerns that open opposition to the initiative, which is a revived version of the Saudi initiative approved at the 2002 Arab League summit in Beirut, will cause friction between Hamas and the Saudis. The initiative offers Israel normalization of relations with the Arab world in exchange for a full withdrawal to 1967 lines and a negotiated settlement to the Palestinian refugee problem.
Israel and the United States have not rejected the initiative but expressed reservations on such Israeli red line issues as the refugees problem. When asked whether Hamas will accept the initiative, senior officials in the group said they reject some of its principles.
The spokesman for Hamas in the Palestinian parliament, Salah al-Bardawil, told Haaretz, "we will not agree to recognition of Israel or peace with it [as it appears in the initiative]. We have no problem with the part of the initiative that calls for the establishment of a Palestinian state on the 1967 borders and the right of refugees to return."
Bardawil told Haaretz that Meshal had promised to Saudi King Adbullah that Hamas will work with the Arab consensus view, but "we cannot recognize Israel or agree to peace and normalization."
Meshal called on Arab leaders participating in the summit not to make concessions on refugees and the Palestinians' right to defend themselves, according to Saudi media.
"Meshal called on Arab leaders meeting in Riyadh to adopt a strategy based on the right to self-defense," the official Saudi news agency SPA said. "He said that conceding legitimate rights such as the right of return and the Palestinian people's right to protection was unacceptable," the report added.
Meshal spoke to SPA in Algeria, after a visit to Saudi Arabia for talks with officials there on Sunday.
Taking a more severe position, Ismail Radwan, a Hamas spokesman in the Gaza Strip, declared Tuesday that "the Hamas positions have not changed in any way. The new government has accepted commitments but our positions remain unchanged."
Another Hamas spokesman in Gaza, Fawzi Barhum, told Haaretz that "the issue is not a 'yes' or 'no' by Hamas regarding the initiative. We respect the Arab efforts to attain Palestinian rights and we will act within the Arab consensus. Nonetheless, the Zionist enemy continues to reject the initiative and we will not determine our position in reference to it before it has been accepted."
Meanwhile, President Mahmoud Abbas is expected to announce the Palestinian Authority's support for the initiative. Prime Minister Ismail Haniyeh of Hamas is not expected to present the unity government's views on the initiative.
Abbas: Arab plan offers Israel chance to live in 'sea of peace'
The Arab peace plan could be Israel's last chance to live in a "sea of peace" and should not be squandered, Palestinian Authority Chairman Mahmoud Abbas said on Tuesday.
"This initiative simply says to Israel 'leave the occupied territories and you will live in a sea of peace that begins in Nouakchott and ends in Indonesia'," he said, referring to the Mauritanian capital in West Africa and the southeast Asian country that is the world's most populous Muslim country.