The U.S. military plans to change the focus of its Afghanistan mission from combat to training local forces in 2013, Defense Secretary Leon Panetta said Wednesday.

BRUSSELS, Belgium — Defense Secretary Leon Panetta said Wednesday that U.S. forces would step back from a combat role in Afghanistan as early as mid-2013, more than a year before all U.S. troops are scheduled to come home.

Panetta cast the decision as an orderly step in a withdrawal process long planned by the United States and its allies, but his comments were the first time America had put a date on stepping back from its central role in the war. His words reflected the Obama administration’s eagerness to bring to a close the second of two grinding ground wars it inherited from the Bush administration.

Promising the end of the U.S. combat mission in Afghanistan next year also would give President Obama a certain applause line in his re-election campaign speeches.

Panetta said no decisions had been made about the number of U.S. troops to be withdrawn in 2013, and he made clear that substantial fighting lies ahead. “It doesn’t mean that we’re not going to be combat-ready; we will be, because we always have to be in order to defend ourselves,” he said on his plane on the way to a NATO meeting in Brussels, where Afghanistan is to be the focus.

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Some 90,000 U.S. troops are in Afghanistan, but 22,000 are due home by fall. No schedule has been set for the pace of the withdrawal of the 68,000 who will remain, other than pledges that all are to be out by the end of 2014.

Panetta offered no details of what stepping back from combat would mean, saying the troops would move into an “advise-and-assist” role to Afghanistan’s security forces. Such definitions typically are murky, particularly in a country such as Afghanistan, where U.S. forces are spread widely among small bases across the desert, farmland and mountains, and where the native security forces have a mixed record of success.

Commanders will note there’s no such thing as a noncombat soldier, and U.S. troops continued to suffer losses in Iraq, even after the mission there switched from combat to what the Pentagon dubbed an “advise-and-assist” role.

The defense secretary offered the U.S. withdrawal from Iraq as a model. U.S. troops there eventually pulled back to large bases and left the bulk of the fighting to the Iraqis.

Panetta said the NATO discussions also would focus on a potential downsizing of Afghan security forces from 350,000 troops, largely because of the expense of maintaining such a large army. The United States and other NATO countries support those forces at a cost of about $6 billion a year, but financial crises in Europe are causing countries to balk at the bill.

“The funding is going to largely determine the kind of force we can sustain in the future,” Panetta said.

He and his team played down last week’s announcement by French President Nicolas Sarkozy that his country would break with its NATO allies and accelerate the withdrawal of its forces in Afghanistan by pulling back its troops a year early, by the end of 2013. Pentagon officials said Sarkozy and the United States might be more in tune than it appeared, although they acknowledged confusion about the French president’s statement and said their goal was to sort it out at the NATO meeting Thursday.

Sarkozy made the announcement after an attack by a rogue Afghan soldier killed four unarmed French soldiers on a training mission. There have been similar incidents of Afghan troops’ killing U.S. forces, most recently involving the death of a Marine in Helmand province Wednesday.

Panetta said he would seek to reassure NATO that, although budget constraints and a focus on Asia were forcing the United States to withdraw two combat brigades — as many as 10,000 troops — from Europe, it was not abandoning its allies. The U.S. military, he said, would try to make up some of the difference by rotating more troops in for training exercises in Europe.

Information from McClatchy Newspapers is included in this report.