Iraq's Sunni Arabs are unlikely to muster the votes needed to defeat the country's new draft constitution in an October referendum, Vice President Ghazi Yawar, the highest-ranking Sunni Arab in the transitional government, said Monday, as hundreds of Sunnis rallied against the charter for a second week, and an American soldier was killed when hostile fire forced down an Army helicopter.

Sunni Arabs should look ahead instead to parliamentary elections in December and concentrate on winning enough seats to change the way the constitution is implemented, Yawar said.

"In the street there is too much tension, too much bitterness, and I think many people will push for a negative vote," Yawar, a tribal leader from the north who was president in Iraq's previous government, told a small group of Western reporters in his gilt villa inside Baghdad's fortified Green Zone.

But "I think it will be extremely hard to defeat," Yawar said. "That's why I think we have to aim at the next elections. . . . Whoever feels grievance now has to work harder in order to be in the next" government.

Yawar spoke the day after Iraq's Shiite- and Kurdish-led government and the United States announced completion of the draft constitution, sending it to a national vote by Oct. 15. Sunni Arab negotiators on the constitution committee refused to endorse it and stood by glumly Sunday as Shiite and Kurdish leaders beamed at a celebratory ceremony.

The constitution's provision for creation of federal states under a weak central government has angered members of the traditionally nationalistic Sunni Arab minority, who say it will lead to the breakup of Iraq.

The Sunnis object most strongly to a proposal by the Supreme Council for the Islamic Revolution in Iraq, a Shiite religious party that has a leading role in the coalition government. The proposal, raised by Supreme Council leader Abdul Aziz Hakim this month, called for formation of what would be an oil-rich, predominantly Shiite federal region in the south made up of half of Iraq's 18 provinces.

While the controversy over federalism has spurred more Iraqi Sunnis to join the political process than at any time since the U.S.-led invasion in 2003, the foreign-led Sunni insurgent group headed by Abu Musab Zarqawi has threatened to kill any Sunni who votes on the charter.

The insurgent threats and government delays in opening registration centers in the Sunni-populated west likely would mean only one province, Anbar, could muster the votes needed to reject the constitution, Yawar said Monday. Two-thirds of voters in at least three provinces must reject the draft charter for it to fail.

Rejection of the draft proposal would mean Iraqis would have to elect another transitional government to try again to write a constitution. Yawar, like some Shiites and Kurds, said another weak transitional government would only open the way for more political violence.

While Shiites and Kurds have clear leaders, neither Yawar nor any other Sunni Arab official commands a dominant bloc.

Iraq's disaffected, disempowered Sunni Arabs have vowed not to repeat their boycott of January's elections, which brought the current Shiite- and Kurdish-led government to power.

On Monday, hundreds on Sunni Arabs marched in Saddam Hussein's home area of Tikrit, some carrying pictures of the toppled leader. Others clutched posters with slogans declaring, "No to the Zionist-American-Iranian constitution!" according to news agencies.

In the heavily Sunni western city of Ramadi, Anbar's provincial capital, hundreds rallied to demand that the government open more voter registration centers. With a Sept. 1 deadline looming to register, only 19 of the 28 centers in Anbar have opened, although the national election commission said Monday that it would extend registration there until Sept. 7.

Ali Omran, a 41-year-old demonstrator in Ramadi, said people in his village had to drive more than two hours through U.S. military checkpoints to sign their names to voter rolls. "We consider this a conspiracy," Omran said. "They want to strangle us by not allowing us to participate in the referendum, to make it easy for the Kurds and the Shiites to run their draft of the constitution."

"My family will take part in the referendum even if we have to spend the night in the street by the voting center," said another demonstrator, Mariam Mohammed, a 32-year-old university instructor.

In Baghdad, Reuters demanded that the U.S. military release one of its Iraqi cameraman wounded in the same shooting that killed a soundman working for the news agency on Sunday in west Baghdad. Iraqi police said U.S. soldiers shot the journalists, according to Reuters.

The agency quoted a military spokesman, Lt. Col. Robert Whetstone, as saying U.S. forces were still investigating.

In Tal Afar, an insurgent stronghold 260 miles northwest of Baghdad, a U.S. Army helicopter made a forced landing Monday night under hostile fire, the U.S. military said. One soldier was killed and another injured. Residents of Tal Afar reached by telephone said the helicopter came down about 6:30 p.m. in the southwestern part of the city, the Associated Press reported.

Meanwhile, an Iraqi leader of Zarqawi's al Qaeda in Iraq promised a series of attacks timed to the start of the Muslim holy month of Ramadan in October. The leader, Abu Qudama, said a current lull in bombings was only "the calm before the storm."

Special correspondent Omar Fekeiki contributed to this report.

Protesters, including one with a picture of Saddam Hussein, rally against Iraq's proposed constitution in the ousted president's home area of Tikrit. Rallies elsewhere demanded the government open more voter registration centers.A Sunni woman in Baghdad registers to vote in the referendum on Iraq's proposed constitution. The deadline to register in most areas is Sept. 1.