BAGHDAD, Iraq - Sunni Arab leaders today rejected Shiite calls for a federal Iraq enshrined in the constitution, saying the proposal would fracture the country along religious and ethnic lines. The dispute threatens to delay completion of the charter that is due Monday.

Sunni Arab leaders were responding to a demand by a leading Shiite lawmaker for provisions in the constitution to allow local Shiite control in the southern and central parts of the country. Sunni Arabs fear they will lose out on oil revenues if the country is split into federated zones.

"We reject it wherever it is, whether in the north or in the south, but we accept the Kurdish region as it was before the war," said Kamal Hamdoun, a Sunni member of the committee drafting the constitution. Some Shiite leaders want to replicate the success of Kurdish leaders in the north who govern an autonomous part of the country.

"The aim of federalism is to divide Iraq into ethnic and sectarian areas. We will cling to our stance of rejecting this," Hamdoun said.

Meanwhile, a U.S. Apache helicopter crashed today in northern Iraq, injuring two U.S. troops, and a roadside bomb killed an American soldier in the central city of Tikrit, the military said.

The two injured servicemembers were being evacuated in the area of Kirkuk, 180 miles north of Baghdad, said Staff Sgt. Duane Brown, a spokesman for the 42nd Infantry Division. He said the helicopter crash was under investigation.

In central Iraq, a U.S. soldier was killed today in a roadside bombing while on patrol in Tikrit, 80 miles north of Baghdad, the U.S. military said. The soldier, whose name was not released, was assigned to Task Force Liberty.

During a speech Thursday to cheering crowds in Najaf, Abdul-Aziz al-Hakim, leader of the country's biggest Shiite party, called for a Shiite federal state, saying it was needed "to keep a political balance in the country" after decades of dictatorship under Saddam Hussein.

Al-Hakim's call may have been a last-minute bargaining tactic; Sunni Arabs immediately rebuked the proposal.

"We were surprised with Abdul-Aziz al-Hakim's declarations today," said Saleh al-Mutlaq, a Sunni member of the commission that is drafting the commission. "Time is running out and such declarations should be much more calm. We don't have time for such maneuvers."

Al-Mutlaq and other Sunnis had suggested that a decision on federalism should be delayed until a new parliament is elected in December. That parliament is expected to have more Sunni Arab members than the current one because many Sunnis boycotted the January election.

The incorporation of Sunni Arabs into the political process is seen as central to undermining the insurgency.

Al-Hakim's endorsement could pave the way for a Shiite south and a Kurdish north. The Kurds have demanded federalism to maintain control over three northern provinces and also want authority over Kirkuk, from which thousands of Kurds were expelled by Saddam.

Government officials urged compromise after al-Hakim's speech. "Every group is saying that they have stands that they cannot abandon because they are 'red lines' but in the end, everyone is going to make some concessions," presidential spokesman Kamran Qaradaghi said Thursday.

Also Thursday, al-Qaida in Iraq, the country's most feared terrorist group, posted an Internet statement threatening anyone involved in drafting the "illegal constitution" and vowed to attack voting centers during the October referendum.

Al-Hakim is close to Iraq's leading Shiite cleric, Grand Ayatollah Ali al-Sistani, who had been reluctant to support federalism. Al-Sistani conferred Wednesday night with al-Hakim and radical Shiite cleric Muqtada al-Sadr in a bid for Shiite unity.

Although al-Sistani has issued no statement about federalism, an official close to the ayatollah said Thursday his silence should be interpreted as support. The official spoke on condition of anonymity under rules imposed on the ayatollah's entourage.

"The Shiite community feels in danger," the official said. "If Shiites are going to be threatened, they have many cards to play. And if Shiites are going to be sidelined, they will not lie down."