BAGHDAD, Iraq — Sunni Arab leaders angrily rejected early election results on Tuesday, saying the vote had been fixed in favor of Iranian-backed religious Shiites and calling for an investigation into possible fraud. Secular politicians also denounced the results and demanded an inquiry.

The growing fury threatened to build into a protracted confrontation that could delay the formation of the new four-year government.

That process is already expected to take weeks, if not months. American diplomats here are pushing Iraqi politicians to speed up the negotiations so as not to lose momentum from the elections last Thursday.

The rejection of the early results, the first set of which was released on Monday, also raised the possibility that Sunni Arab politicians could boycott the political process, as they have done several times in the last year.

The Bush administration's plans to temper the Sunni-led insurgency and reduce the U.S. troop presence are predicated on Sunni Arabs' entering the new government. Any withdrawal by those politicians would be a serious setback for the White House.

"In order for Iraq to succeed, there has to be cross-ethnic and cross-sectarian cooperation," Ambassador Zalmay Khalilzad, the top American envoy in Iraq, said Tuesday.

The Sunni Arabs' denunciations came despite the election commission's release of new results on Tuesday that showed the main religious Sunni coalition leading in Sunni-dominated provinces.

In all, the early results account for 90 percent of the roughly 10.5 million ballots cast, electoral officials said. But certified results will not be announced until early January because the commission has to investigate about 700 complaints, at least 20 of which are serious, said Adel al-Lami, the commission's general director.

Those inquiries could change the final outcome, Lami said in a telephone interview. He added that early results for the remaining 10 percent of the ballots would not be announced immediately because of inquiries into possible voting irregularities. Teams of Iraqi electoral officials and U.N. advisers have been sent out to scrutinize votes in eight provinces, Lami said.

"We reject the results that have been announced by the electoral commission," Adnan al-Dulaimi, a leader of the Sunni coalition, said at a news conference.

"If the electoral commission doesn't adopt very strict measures against these violations," he added, "we are going to call for another election."

Saleh al-Mutlak, a prominent ex-Baathist heading his own Sunni party, insisted that international groups take the lead in investigating the election.

"We will not remain silent about what has happened, so we call on the international community to intervene," he said at a separate news conference. "We call on the president of the United States not to add another mistake to the mistakes already made in Iraq."