Paris ? Three European powers called Wednesday for a new international conference on Afghanistan, hoping to accelerate and improve training of local forces and lay out a timetable in which Afghans can take back full control of their war-battered country.

Britain’s Gordon Brown, Nicolas Sarkozy of France, and Germany’s Angela Merkel sent a letter to U.N. Secretary General Ban Ki-moon calling for the meeting by year-end to discuss the aftermath of the country’s elections.

The escalation of war and rising allied casualties in Afghanistan have sparked criticism in NATO nations such as theirs about the continued military commitment to a mission nearly 8 years after a multinational coalition toppled the hardline Taliban government and sent its al-Qaida allies into hiding.

Critics say the deaths of civilians in NATO air strikes and allegations of ballot-box stuffing and massive fraud in the recent presidential election are undermining the legitimacy of the Western-backed government in Kabul.

In the letter, dated Tuesday, the three leaders called for “new prospects and goals” in Afghanistan on governance, law, security, and economic and social development. Sarkozy’s office released the letter Wednesday.

“It seems a natural occasion to call for an international conference on Afghanistan before the end of this year right after the inauguration of the new Afghan government,” they wrote.

The letter made no mention of the allegations of electoral fraud.

The conference could build on previous international gatherings on Afghanistan and a strategic review carried out by NATO, they said.

The leaders want to reach agreement on “new benchmarks and timelines,” and “to set our expectations of ownership and the clear view to hand over responsibility step by step to the Afghans, wherever possible.”

“In this context, we should consider to increase the speed, size and quality of training of the Afghan security forces as well as how best to create the proper local environment,” they added.

Ari Gaitanis, a spokesman for the U.N. Peacekeeping Department, said last week the summit would likely take place next spring in Kabul — or later than when Britain, France and Germany want. He said a list of invitees has not yet been prepared.

Klaus Vater, a German government spokesman, said that Berlin also could host the meeting, but that no venue has been yet decided: “There are many places where such a conference could take place.”

The letter came as NATO Secretary-General Anders Fogh Rasmussen on Wednesday said he was worried about growing public skepticism about the war effort in Afghanistan, and urged the Afghan government to take greater responsibility for issues ranging from security to good governance.