Afghan President Hamid Karzai is warning there will be no hope for peace in his country without help from its neighbors in fighting terror groups.

Mr. Karzai told diplomats at an international conference in Turkey Wednesday that terrorist networks still are a major threat to Afghanistan’s security. He said that groups conducting what he called a “merciless campaign of destruction” inside Afghanistan continue to have sanctuaries outside the country.

Mr. Karzai called on Pakistan to help his country negotiate with the Taliban’s top leadership, which he says is based in Pakistan.

The Afghan leader joined representatives from some 20 countries and aid agencies in Istanbul for a one-day summit focusing on Afghanistan’s security and economic development as foreign troops prepare to leave the country in the coming years.

Mr. Karzai’s comments come a day after a meeting with his Pakistani counterpart Asif Ali Zardari, in which they discussed a joint investigation into the murder of Afghan peace envoy Burhanuddin Rabbani in September.

Mr. Karzai has regularly urged Pakistan to do more against militants. U.S. and Afghan officials accuse Islamabad of sheltering and supporting insurgents, including the Haqqani network blamed for Rabbani’s death — a claim the Pakistani government strongly denies.

France, Germany, Iran and India are among the countries taking part in the conference.

Turkish President Abdullah Gul said Wednesday that countries have an obligation to contribute to Afghanistan’s peace, stability, security and wealth. He says such cooperation is necessary for the “sake of our common interests.”

The summit in Istanbul is expected to lay the groundwork for the way forward in Afghanistan. International combat troops are set to complete their withdrawal from the country and transfer full security control to their Afghan counterparts by the end of 2014.

There are more than 130,000 foreign troops in Afghanistan, most from the United States.