Afghan President Hamid Karzai on Tuesday appealed to Pakistan for help in the investigation of the assassination of an Afghan peace envoy, and said efforts to talk directly to the Taliban are futile as long as the insurgents show no desire to negotiate in good faith.

Karzai spoke after a meeting with his Pakistani counterpart, Asif Ali Zardari, and one day ahead of a regional conference on security and economic development in Afghanistan, which has endured a series of high-profile assaults in the Kabul area in the last few months.

One of those attacks was the Sept. 20 assassination of Burhanuddin Rabbani, a former Afghan president and peace council leader who was killed at his Kabul home by a suicide bomber posing as an emissary from the Taliban. Some Afghan officials accused Pakistan and its spy agency of supporting the militants who killed him, alleging Taliban leaders based in the Pakistani city of Quetta were involved.

"We cannot keep talking to suicide bombers," Karzai said. "Therefore we have stopped talking about talking to the Taliban until we have an address for the Taliban, until we have a telephone for the Taliban, until we have a door that we can knock on.... We have been hurt badly. Our desire for peace has been either misunderstood or misused."

Karzai said he and Zardari, along with Turkish President Abdullah Gul, agreed on a joint inquiry into Rabbani's death.

"We have evolved a mechanism that I hope will give us the results," Karzai said.

Gul said the intelligence services of all three countries are discussing the Rabbani investigation.

"We reached a common understanding and we will take further steps in the days to come," said Gul, who has hosted the Afghan and Pakistani leaders in the past.

At Wednesday's conference, diplomats will campaign for a stable Afghanistan after the planned withdrawal of international combat forces by the end of 2014, a goal imperiled by militant attacks, a weak Afghan government and the conflicting interests of regional players.

Karzai said there are many problems and threats against countries in the region, and he urged the nations to cooperate with honesty, his office said. In Istanbul, Afghanistan and Pakistan signed cooperation agreements, including conducting joint military drills.

Afghanistan and the United States are demanding that Pakistan do more to curb militant activity and sanctuaries on its territory. Pakistan denies it shelters or supports the Haqqani network, a Taliban wing blamed for an attack on the U.S. Embassy in Kabul in September and other deadly operations.

The title of the meeting Wednesday is "Security and Cooperation in the Heart of Asia," yet diplomats in Afghanistan, regional countries and the West have downplayed expectations.

Fourteen regional countries are to be represented: Afghanistan, China, India, Iran, Kazakhstan, Kyrgyzstan, Pakistan, Russia, Saudi Arabia, Tajikistan, Turkey, Turkmenisan, Uzbekistan and the United Arab Emirates.

Germany, France and other Western countries with troops deployed in Afghanistan were sending envoys to show support. U.S. Secretary of State Hillary Rodham Clinton had planned to attend, but canceled her trip to be at the side of her mother, who was ill. On Tuesday, Dorothy Rodham died in Washington.

Iran, at odds with the international community over its nuclear program, is sending its deputy foreign minister, Mohammad Ali Fathollahi.

Afghanistan's broader aims were not likely to be achieved in Turkey.

The war-weary nation wants countries to sign confidence-building measures, such as exchanging information on defense spending and numbers of troops deployed on borders; visiting military bases; pledging not to violate territorial integrity or interfere in the internal affairs of sovereign states; relaxing visa requirements; expanding trade; and cooperating on border management.

A senior U.S. administration official said the regional countries are expected to reiterate a commitment to sovereignty, endorse a transition to Afghan security leadership, endorse Afghan efforts for a political solution to the war and help Afghanistan develop a sustainable economy. The official briefed reporters on condition of anonymity because of the sensitivity of the discussions.

Clinton was in Pakistan earlier this month to press the nation to send its army after militants the U.S. says get special protection from the Pakistani government, while making the case that Pakistan should use its influence with Taliban militants to encourage peace in Afghanistan.

Pakistan has deployed 170,000 soldiers to its eastern border with Afghanistan and more than 3,000 soldiers have died in battles with militants. Pakistani leaders bristle at U.S. criticism that they have not done enough or that they play a double game, fighting militants in some areas and supporting them in others where they might be useful proxies in a future conflict with India, its archenemy.

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Deb Riechmann reported from Kabul, Afghanistan.