BAGHDAD, Iraq – Thousands of people paid respects Friday to Abdul Sattar Rishawi, the slain sheik credited with forging ties between Sunni tribesmen and the U.S. military, and American leaders mulled the prospects of the brother expected to succeed him.

The U.S. military also reported that four U.S. soldiers were killed in Diyala province by an explosion near their vehicle. No names were released pending notification of their families, and no further details were available.

The insurgent group al-Qaida in Iraq on Friday claimed responsibility in a W eb site posting for the killing of Rishawi, who had persuaded Sunni tribes that once backed the insurgents to accept U.S. cooperation and arms to fight them.

His killing Thursday by a bomb outside his home was a setback to U.S.-led efforts in the western province of a l- Anbar, which President Bush has used as a measure of success in the military build-up that began earlier in 2007.

Rishawi’s older brother, Ahmed, will reportedly take over leadership of Rishawi’s tribal coalition, known as the al- Anbar Awakening Council . He lashed out against the insurgents for the killing.

“We are going to continue our fight and avenge his death,” Ahmed said.

At the Pentagon, Col. Sean B. MacFarland predicted that after Rishawi’s death , others would vie for increased influence over the movement, known as al- Anbar Awakening Conference, but that they would remain U.S. allies.

“There will be a different kind of leadership,” he said, more diffuse but still united.

MacFarland, as commander of the 1st Armored Division’s 1st Brigade, led U.S. forces in the provincial capital of Ramadi in 2006 and helped broker the deal between U.S. forces and Rishawi last September.

“He saw his opportunity for revenge and he took it,” he said, with Rishawi persuading other leaders of the fiercely independent Sunni tribes in the region to rally to his side.

The two Rishawi brothers were a striking contrast, said MacFarland: Abdul Sattar in traditional clothing, a charismatic risk-taker; and the older, college-educated Ahmed in Western-style suits, a businessman and deal- maker.

Rishawi’s critics said he took too much credit for turning back the insurgents in al- Anbar and that his ambition alienated other tribal leaders. He had traveled earlier this summer to Baghd ad to meet with Shiite leaders.

Ahmed, who holds a degree in political science, “will have more of a consensus type of approach where Rishawi was more, “My way or the highway,”‘ said MacFarland.

Rishawi, already praised as a martyr, will have a lasting influence, he said: “more powerful in death than in life.”

An estimated 1,000 people attended Rishawi’s funeral Friday, paying respects to one of the few Sunni tribesmen who saw the value of reaching across sectarian lines. He had hoped to use his successes in al- Anbar as the base for a national party.

Mourners included the defense and interior ministers of Iraqi Prime Minister Nouri al- Maliki’s Shiite-dominated government.

“Rishawi is a national hero,” said national security advise r Mowaffak Rubaie.

President Bush sent his condolences through the U.S. Ambassador in Jordan.

Rishawi knew he was on dangerous ground, throwing his lot with U.S. forces and even posing with President Bush last week during a visit to Iraq. But he kept any fears he had hidden.

“I’m not scared,” he said, acknowledging in June that he was a marked man. “The only thing that scares me is not being right.”

Suspicious fingers have been pointed in all directions over the bombing on the outskirts of Ramadi, about 60 miles west of Baghdad. Sectarian and ethnic rivalries have caused tens of thousands of deaths with lines of conflict blurred by personal ambition, jealousies and religious extremism.

The Islamic State of Iraq, an umbrella organization that includes al-Qaida in Iraq, claimed it had planned the killing for a month, a punishment for collaborating with Americans, according to the posting on the W eb site.

“You cannot eliminate the possibility that it was a homegrown effort by those political opponents within Iraq who are concerned about the growing political power of the Sunnis,” said retired Army Gen. William Nash, now at the Council on Foreign Relations.

But, added Nash, the killing could also have been an inside job carried out by Sunni insurgents planting someone inside Rishawi’s circle.

“Rishawi has security all over his place, therefore it was either a breach … or it’s an inside job,” said Louai Dulami, Rishawi’s office manager. “It’s practically impossible to infiltrate the area where he was killed.”

Also Friday, seven police reportedly were killed in the northern city of Baiji when a truck bomb blew up at a police checkpoint. In Fallujah , west of Baghdad, one police officer was killed and two injured by a remote-controlled bomb planted near their car. And in Kirkuk, an Iraqi army officer was fatally shot in front of his house.