The leaders of Afghanistan and Pakistan are meeting for the first time since the killing of Afghanistan's main peace negotiator, an attack that raised tensions between the neighboring nations.

Turkish President Abdullah Gul is hosting talks between Afghan President Hamid Karzai and Pakistani President Asif Ali Zardari in Istanbul.

The meeting comes a day ahead of an international conference in Afghanistan and amid demands by U.S. and Afghan officials that Pakistan do more to target militant sanctuaries on its territory.

Afghanistan also suspects Pakistani involvement in the September killing of Afghan peace envoy and former president Burhanuddin Rabbani. Pakistan denies the charge.

On Tuesday, President Karzai and President Gilani held separate talks with Turkey's president before a trilateral meeting. Turkish diplomats said Turkey hoped to resolve some of the differences between Afghanistan and Pakistan so that both countries could work together towards peace in Afghanistan.

Afghanistan and Pakistan were also expected to sign a security cooperation agreement.

Tuesday's meeting will be followed by a regional conference on Afghanistan attended by leaders from 14 countries, including France, Germany and India.

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 ill health of her mother.