The elderly former Afghan president tasked with persuading the Taliban to stop fighting was in Dubai on Tuesday when he received an urgent call. Taliban leaders were ready to talk peace, an associate told him. He was needed in Kabul right away.

It sounded like the sort of breakthrough that Afghan and Western leaders have been desperately seeking to end a war that has destroyed wide swaths of the country and cost the United States dearly in treasure and blood.

But hours later, Burhanuddin Rabbani was dead, killed in his home by the supposed Taliban negotiator whom he had rushed back to Kabul to meet. The assassination claimed the leader of Afghanistan’s fledgling peace council and dealt a powerful blow to hopes that the war can be settled at the negotiating table rather than on the battlefield.

Rabbani is just the latest in a series of Afghan leaders who have been killed this year. His death offered a vivid retort from insurgent commanders to suggestions that they should talk with an Afghan government that is rife with dysfunction at a time when foreign troops are starting to pull out.

The attack also became the latest reminder that nearly a decade after U.S. troops helped to topple the Taliban regime in Kabul, the insurgency remains capable of carrying out strikes even in the most fortified sections of the capital.

“The face of the peace initiative has been attacked,” U.S. Marine Gen. John Allen, the top NATO commander in Afghanistan, said in a statement Tuesday night. “This is another indicator that, regardless of what Taliban leadership outside the country say, they do not want peace, but rather war.”

U.S. officials have long said they believe that insurgent leaders are based in Pakistan, and Tuesday’s attack will probably intensify calls for the Pakistani government to take a stronger stand against militants who operate near the border.

The bombing came a week after insurgents armed with grenades, rifles and rockets attacked the U.S. Embassy and nearby installations in Kabul for 20 hours. U.S. officials said the siege was probably carried out by the Haqqani network, a well-trained faction of the Taliban that has been linked to several spectacular attacks in the Afghan capital and that is based in the tribal areas of Pakistan.

The attack on Rabbani appears to have succeeded because a trusted former senior Taliban official who reconciled with President Hamid Karzai in 2005 facilitated the meeting, according to Bashir Bezhan, a friend of Rabbani’s.

Rahmatullah Wahidyar, who served as a deputy government minister when the Taliban was in power in the late 1990s and sits on the peace council, had vouched for the assailant, Bezhan said.

“You have to come and meet this guy,” Bezhan said Rabbani was told by associates urging him to return to Kabul.

Mohammad Masoom Stanekzai, another senior member of the peace council, accompanied Wahidyar in escorting the supposed Taliban negotiator through the maze of checkpoints, blast walls and gates that lead to Rabbani’s house.

The guest, who had not been searched, lowered his head as he approached Rabbani, moving in for a hug, according to Afghan security officials. A thundering blast — apparently emanating from a bomb hidden beneath the attacker’s turban — ended the meeting before it began.

Rabbani, said Gen. Abdul Zahir, a senior police official, “was killed on the spot.”

The two peace council members were wounded in the attack, Zahir said. It was unclear whether Wahidyar knew of the assailant’s plan.

Karzai was in New York preparing for the U.N. General Assembly meeting at the time of the attack, but he cut his trip short and was on his way back to Afghanistan.

“We will miss him very, very much,” a solemn Karzai said of Rabbani during brief remarks he made alongside President Obama. “I don’t think that we can fill his place easily.”

Obama called the death a “tragic loss,” albeit one that would not deter the Afghan government and its Western allies “from creating a path whereby Afghans can live in freedom and security and prosperity.”

The first phase of the U.S. pullout from Afghanistan began this month. NATO nations say they intend to complete their combat mission in the country by the end of 2014.

Rabbani, who was in his 70s, was an unusual choice to lead reconciliation talks with the insurgency. Many in Afghanistan reviled him for his divisive role during the civil war that devastated Kabul and much of the rest of the country in the 1990s. Rabbani became Afghanistan’s president in 1992 but was forced to flee when the Taliban wrested control of the capital in 1996.

When Karzai picked the ethnic Tajik to lead the peace council last September, many Afghans wondered why the Taliban, which primarily draws support from Pashtuns, would be willing to trust Rabbani. But he was well regarded by non-Pashtuns for his role as leader of the Northern Alliance, which had battled the Taliban throughout its rule.

“He wanted to make this a national process and wanted the approval of all factions in the country,” said Afghan political analyst Haroun Mir. “He could not make peace only with Pashtun leaders.”

The 68-member High Peace Council has accomplished little. Taliban leaders have said they will not negotiate while foreign troops remain in the country.

U.S. officials have backed the peace process, although they have long been skeptical of the Taliban’s readiness to negotiate. U.S. officials have opened back-channel talks with representatives of Taliban leaders, an effort designed to set conditions for formal talks. But those efforts, too, have appeared to gain little traction.

The normally soft-spoken Rabbani had tough words for the Taliban in a speech delivered several weeks ago. He called the group’s attacks a “disgrace,” carried out by militants claiming to be acting in the name of Islam.

Rabbani’s assassination was reminiscent of the suicide bombing that killed Ahmed Shah Massoud, the revered Afghan commander who was long allied with Rabbani and who helped lead the insurgency that ultimately drove Soviet occupation forces from Afghanistan in 1989. Massoud was killed two days before the Sept. 11, 2001, terrorist attacks by two al-Qaeda operatives posing as journalists and carrying hidden bombs.

Special correspondents Javed Hamdard and Sayed Salahuddin in Kabul and staff writer William Branigin in Washington contributed to this report.