A global conference on Afghanistan's future has opened in the German city of Bonn.

Delegates from more than 80 countries focused Monday on charting a course for the war-torn country after international combat troops leave in 2014. But Pakistan, considered vital to any prospect of stability in Afghanistan, is boycotting the meeting in response to a cross-border attack by NATO late last month that killed 24 Pakistani soldiers.

The talks in the former German capital are expected to address three key areas, including the transfer of security responsibilities from international to Afghan forces, reconciliation with the Taliban, and long-term prospects for international aid.

On the eve of the conference, Afghan President Hamid Karzai criticized Islamabad for its lack of help in achieving reconciliation. In an interview Sunday with the German weekly Der Spiegel, Mr. Karzai said that “until now Pakistanis have refused to help with talks with the Taliban leadership.”

The Afghan leader also appealed for continued financial and military support for his nation after 2014. He said Afghanistan will be more than ever on the frontline, warning that “if we lose this fight, we are threatened with a return to a situation like that before September 11, 2001.”

Among the delegates attending the Bonn conference are U.N. Secretary-General Ban Ki-moon and U.S. Secretary of State Hillary Clinton.

Mr. Ban on Sunday lamented Pakistan's absence, while also promising Kabul the international community's long-term support. A senior State Department official called Pakistan's boycott “regrettable,” but said it till not impact the conclusions of the conference in any way.

The U.S. ambassador to Afghanistan, Ryan Crocker, said Pakistan's absence is “unfortunate,” but will not derail Afghan progress or change the outcome of the gathering.

The talks in Bonn are taking place 10 years after a conference, also in Bonn, to appoint a transitional government in Afghanistan.