Afghan President Hamid Karzai on Tuesday rejected further talks with the Taliban, saying “we cannot keep talking to suicide bombers.”

President Karzai told reporters in Turkey that his government would instead continue to talk with Pakistan about finding solutions to the insurgency-related violence.

The Afghan leader's comments followed a meeting with Pakistani President Asif Ali Zardari and Turkish President Abdullah Gul in Istanbul.

Turkey has been trying to facilitate a thaw in the tense relations between the two South Asian neighbors, and appears to have made some progress.

Mr. Gul said Tuesday the two neighbors agreed to combine resources to investigate the killing of Afghanistan's main peace negotiator.

Afghan officials suspect Pakistani involvement in the September killing of Afghan peace envoy and former president Burhanuddin Rabbani, a charge Pakistan denies.

Afghan President Karzai said Tuesday he hopes the joint investigation will produce results.

Earlier Tuesday, Afghan Deputy Foreign Minister Jawed Ludin told Reuters that Pakistan needed to prove it can be trusted. He said Islamabad must “move beyond words” and address Kabul's security concerns.

The meeting between the leaders of Afghanistan and Pakistan was the first since Rabbani's death, and comes just a day before leaders from 14 countries, including France, Germany and India, gather for a key regional conference.

Foreign ministers will focus on security and economic development in Afghanistan as foreign combat troops reduce their presence in the country and completely pull out by the end of 2014.

U.S. Secretary of State Hillary Clinton was set to take part in the conference, but cancelled her visit to Istanbul because of the death of her mother.

Afghan and Pakistan military leaders have also been meeting in Istanbul, and the two nations were expected to sign a security cooperation agreement.

Turkish diplomats had said Turkey hoped to resolve some of the differences between Afghanistan and Pakistan so that the two countries could work together towards peace in Afghanistan.