BAGHDAD, Iraq -- In a dramatic shift, the U.S. ambassador yesterday raised the possibility 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 yesterday, U.S. warplanes struck three suspected al-Qaida targets near the Syrian border, killing what the U.S. military called a "known terrorist." Iraqi officials said 45 people died, most of them in fighting between an Iraqi tribe that supports the foreign fighters and another that opposes them.

The nation's Sunni Arabs 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 told reporters that he believed that "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 yesterday 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.

The Interior Ministry has denied targeting Sunnis.

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.

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 yesterday, the Defense Department announced that a U.S. 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 yesterday 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.