UNITED NATIONS — Secretary-General Ban said yesterday that the United Nations should “explore” the creation of an “international presence” in Gaza, where a Palestinian Arab civil war intensified yesterday as Hamas fought to complete its victory over Fatah and seize control of the strip.

The idea of sending a multinational force to Gaza, while only in an early stage, has gained momentum in recent days: Israel’s Prime Minister Olmert has mentioned it in several occasions, as has President Abbas of the Palestinian Authority.

But a new tendency in Jerusalem to rely on international institutions was put to a test yesterday as an internal report highly critical of U.N., Israeli, and American policies, written on May 5 by a former top U.N. policymaker for the Middle East, Alvaro de Soto of Peru, was leaked to the Guardian in London.

U.N. officials and Mr. de Soto himself characterized the report as “end of mission” ruminations by an outgoing official. Mr. de Soto, however, has long advocated distancing the organization from Washington’s policies.

The “current U.S. administration probably has neither the political will nor the political capital at home, abroad, or in the region to sustain genuine leadership,” in the Middle East, Mr. de Soto wrote to Mr. Ban in an previously unpublished internal memo from January seen by The New York Sun. The Bush administration is “constrained by its ideological predisposition towards Israel and its overriding concern with terrorism,” he added.

One of the main points of Mr. de Soto’s criticism is opposition to the American-led policy attempting to neutralize Hamas.

Meanwhile, Hamas yesterday blew up a Fatah-controlled security headquarters in the south Gaza town of Khan Yunis, according to the Daily Telegraph. Since Sunday, at least 69 Palestinian Arab combatants and civilians have been killed in this latest wave of an armed struggle between the two political factions, as well as in battles among familial clans and turf wars between armed gangs.

“Any place that commits any kind of aggression against Hamas has to be targeted,” said a Hamas spokesman, Fawzi Barhoum. The Iranian and Syrian-backed group, defined by America as a terrorist organization, has marked important military victories this week in the increasingly bloody clashes in Gaza, which have begun to spill into the West Bank as well.

On Tuesday, Mr. Abbas suggested that a multinational force might help calm the violence: “I had a telephone talk with President Abbas” Tuesday, in which “he raised this issue to me, to consider this issue,” Mr. Ban told the Sun during a press encounter after a monthly luncheon with Security Council ambassadors.

“This is an idea” for “which we need to explore the possibilities,” Mr. Ban said, adding he had discussed it with the council members at the luncheon. But international observers or troops would be only sent to Gaza, he said, after decisions are made as to “where to locate them, what would be the terms of reference, what would their missions be.”

Top Israeli officials have also publicly pondered the international force idea several times recently. Mr. Olmert, who is scheduled to meet the Mr. Ban for lunch in New York Sunday, said that such a force might be deployed on the Egyptian border with Gaza in an area known as the Philadelphi Route, where illicit weapons are smuggled.

The battling Gaza factions are not eager to allow outside forces to come in, however. “Deployment of a force always has to be based on the agreement of all parties,” the undersecretary-general for peacekeeping, Jean Marie Guehenno, said.

“If Israel wants an international force deployed on its side of the border, that’s fine,” Egypt’s ambassador to the United Nations, Maged Abdelaziz, told the Sun. But he added that Egypt, the only outside power with a military presence in Gaza, would oppose an international force there. Egypt’s Foreign Minister Ahmed Aboul-Gheit has already rejected Mr. Olmert’s suggestion for an international force to be deployed along the Phildadelphi Route, he noted.

It is also far from clear that there are many international volunteers to go to Gaza.

“I don’t think it’s possible for the Security Council to take action in this regard,” China’s ambassador to the United Nations, Wang Guangya, said.

At the Secretariat, the talk of the building was Mr. de Soto’s leaked report, in which he advocated ending the U.N. participation in the so-called “quartet,” a Middle East steering group that also includes America, Russia, and the European Union. He also accused a former prime minister of Israel, Ariel Sharon, of leaving Gaza in 2005 in order to put “formaldehyde” on the two-state plan known as the “Road Map to Peace,” and criticized the American-led boycott of the Palestinian Authority after the Hamas election victory.

The report was seen by some as Mr. de Soto’s parting shot, made after losing out to advisers who are less opposed to Washington.

“It is to Ban’s credit that he invited all factions in the policy debate,” said a long-time consultant to the U.N. executive office, Eve Epstein. “In the end, he showed strength and did not succumb to reflexive America-bashing.”