Afghanistan's grand council appears to favor setting up a strong presidency, the U.S. ambassador here said Saturday in his first assessment of the ongoing closed-door debate over forming the nation's constitution.

Zalmay Khalilzad (search) also rebutted suggestions from the United Nations that attacks by Taliban and Al Qaeda rebels have derailed plans for June elections, the next stage in the two-year drive to stabilize the country.

Some 500 delegates to the constitutional loya jirga (search), or grand council of provincial representatives, have spent a week discussing the country's first post-Taliban charter. President Hamid Karzai (search) said Saturday he hoped the council, meeting in an enormous tent on a Kabul college campus, would finish its work by the end of the year.

Officials have been tight-lipped about the closed, article-by-article discussions of issues such as human rights and how to divide power in a country used to fighting for it. But Khalilzad said after meeting with Karzai that early voting at the jirga indicated a majority supported a strong chief executive.

"At this stage, it looks like there is a preference for a presidential system," he told reporters.

A tolerant Islamic state under a strong presidency is central to the draft constitution put before the delegates by Karzai's U.S.-backed government. Karzai argues that the country needs stable leadership to rebuild after decades of war.

Others back a parliamentary system with an influential prime minister, and express mistrust about Karzai's ambitions.

Khalilzad said attempts to "blur the line" by handing major powers to a parliament had not gathered majority support: "I think that has been rejected."

Earlier Saturday, Karzai himself reported "very good progress," and expressed relief that so far there had been no serious attacks against the meeting as feared. He said the council should take as much time as it needs.

Three rockets slammed into Kabul early Tuesday morning, but none landed near the jirga site or caused serious damage. The U.S. commander in Afghanistan, Lt. Gen. David W. Barno, told The Associated Press on Saturday he expects more attacks.

Calls for more regional autonomy also appeared doomed, said Khalilzad, who has repeatedly met with delegates privately and on the sidelines of the convention.

"It's still out there, but the sense I get from people is that it may not survive."

A delegate from southern Helmand province backed Khalilzad's assessment.

"There was a lot of debate: parliamentary or presidential? But the majority in our committee accept the presidency," Hafizullah Haqyar said by telephone from the jirga site.

Afghanistan is a test case for the United States' ability to build democratic institutions in war-ravaged lands.

Khalilzad said he had stressed to delegates -- including warlords who still hold sway over much of the country -- the need to avoid a breakdown that would jolt the international community, whose funding is crucial for reconstruction.

"We have a lot at stake here and we want Afghanistan to succeed," he said.

Khalilzad reacted sharply when asked about an assessment by the top U.N. official in Afghanistan, Lakhdar Brahimi (search), who said that plans to hold presidential elections in June next year were out of the question because of continued violence.

"We have to see whether the (registration) schedule can be accelerated," Khalilzad said. "It's too soon to decide that June is completely out."

The United Nations, wary after a spate of killings of aid workers across the south and east, says voter registration in troubled areas is now too far behind schedule and elections will likely happen a couple of months later.