In a dramatic shift, the U.S. ambassador raised the possibility Tuesday of further changes to Iraq's draft constitution, signaling that the Bush administration has not given up its campaign to push through a charter that will be broadly accepted.

Also Tuesday, U.S. warplanes struck three suspected Al Qaeda (search) targets near the Syrian border, killing what the U.S. military called a "known terrorist." Iraqi officials said 45 people died, most in fighting between an Iraqi tribe that supports the foreign fighters and another that opposes them.

The nation's Sunni Arabs (search) had demanded revisions in the constitution, finalized last weekend by the Shiite-Kurdish majority over Sunni objections. A Shiite leader said only minor editing would be accepted, because the draft was now ready for voters in an Oct. 15 referendum.

But Ambassador Zalmay Khalilzad (search) told reporters he believed "a final, final draft has not yet been, or the edits have not been, presented yet" — a strong hint to Shiites and Kurds that Washington wants another bid to accommodate the Sunnis.

"That is something that Iraqis will have to talk to each other [about] and decide for themselves," Khalilzad said, speaking alongside a major Sunni Arab community leader who denounced the current draft and accused the Shiite-dominated government's security forces of assassinating Sunnis.

The Bush administration wants a constitution acceptable to all Iraqi factions to help quell the Sunni-dominated insurgency so that U.S. and other foreign troops can begin to go home.

Shiite leaders had no comment on Khalilzad's remarks. As constitution wrangling drew to a close last week, Shiite officials complained privately that the Sunnis were stonewalling and that further negotiations were pointless.

Influential Shiite lawmaker Khaled al-Attiyah, a member of the constitution drafting committee, insisted Tuesday that "no changes are allowed" to the draft "except for minor edits for the language."

Sunnis objected primarily to federalism, which would create Kurdish and Shiite mini-states and threaten Sunni access to oil wealth; purges of former members of Saddam Hussein's Sunni-dominated Baath Party from government; and the description of Iraq as an Islamic but not Arab state, lumping it together with Shiite-dominated Iran.

Shiites consider some of the Sunni demands, especially on the Baath party and federalism, as matters of principle not subject to compromise.

"From a legal point of view, no change can be made to the draft," Shiite negotiator Hussein Athab said. "If (Khalilzad) means legal change, then this is not allowed. If he means political change, I don't know what he means."

But signs were clear that Washington did not feel constrained by legalities and was ready to pressure the Shiites after more than two years of deferring to the Shiite clergy on key steps in Iraq's transition — moves that helped drive apart the Sunnis and the Americans.

Before addressing reporters, Khalilzad warmly introduced Sunni community leader Adnan al-Dulaimi and then stood by as he accused security forces of the Shiite-led Interior Ministry of murdering Sunnis. Al-Dulaimi demanded the resignation of Iraq's interior minister, a member of the biggest Shiite party.

Both Shiites and Sunnis have accused one another of reprisal killings. The Interior Ministry has denied targeting Sunnis.

Sunni Arabs form an estimated 20 percent of the population. They could still scuttle the charter because of a rule that states that if two-thirds of the voters in any three provinces reject the draft, it would be defeated.

Sunnis form the majority in four provinces but their numbers are not so great that they could ensure a two-thirds margin. If voters reject the charter, elections must be held for a new parliament and a new constitution drafted.

Even if the Sunnis lose the referendum, a bitter political battle at a time when the Sunni-led insurgency shows no sign of abating could plunge the country into a full-scale sectarian conflict.

The U.S. airstrikes, which included 500-pound GBU-12 guided bombs, began about 6:20 a.m. in a cluster of towns near Qaim along the Syrian border 200 miles northwest of Baghdad, a U.S. statement said.

It made no mention of tribal fighting but said four bombs were used to destroy a house occupied by "terrorists" outside the town of Husaybah. Two more bombs destroyed a second house in Husaybah, occupied by Abu Islam, described as "a known terrorist," the statement added.

"Islam and several other suspected terrorists were killed in that attack," the statement said. Several of Islam's associates fled his house in Husaybah for the nearby town of Karabilah, the statement said, citing intelligence reports.

"Around 8:30 a.m., a strike was conducted on the house in Karabilah using two precision-guided bombs," the statement said. "Several terrorists were killed in the strike but exact numbers are not known."

Iraqi officials said most of the 45 dead were from the pro-government Bumahl tribe and the pro-insurgent Karabilah tribe, which have clashed before. The Shiite Supreme Council for the Islamic Revolution in Iraq condemned attacks by foreign fighters against "our beloved people" and urged the government to "stop criminals and terrorists from crossing into Iraq."

Also Tuesday, the Defense Department announced that an American soldier was killed three days ago in Tal Afar, a multiethnic insurgent hotbed 260 miles northwest of Baghdad.

The military said an Army helicopter made a "forced landing" late Monday "under hostile fire" near Tal Afar, killing one soldier and injuring another. Videotape obtained Tuesday by Associated Press Television News showed an Apache attack helicopter swooping low over rooftops during a battle when it suddenly spun out of control and plunged behind a group of houses.