Mattis said the Afghan government, which offered talks without preconditions to the Taliban last month, should lead reconciliation efforts with the insurgent factions who have expressed interest in talks.
The United States is picking up signs of interest from Taliban elements in exploring the possibility of talks with Kabul to end the more than 16-year-old war, U.S. Defense Secretary Jim Mattis said on Tuesday.
The defense secretary said he is focused on peace and reconciliation, something that could be mutual as reaching a settlement was "picked up from the Taliban side" even before Ghani's invitation for peace talks.
As part of the so-called South Asia Strategy, the U.S. President Donald Trump in August announced an increase in the number of U.S. troops in the country to push back the resurgent Taliban.
"It has been a game-changer because it has forced every actor to re-examine their assumptions", he said.
"We want the Afghans to lead and provide the substance to the reconciliation effort", Mattis said.
Asked whether the United States would be willing to talk directly with the Taliban, Mattis reiterated the US position that the talks should be led by Kabul.
The United States has in the past also expressed hope of "peeling off" elements of the Taliban and it was unclear how this new effort might be different.
Mattis comments should soften President Trump's stance on refusing to talk with Taliban who for decades have repeatedly terrorized people with violence.
But he said the U.S. was looking for victory in Afghanistan after more than 16 years of conflict, though he said current developments were leading not to a military victory, but "a political reconciliation".
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The insurgent group has said it is prepared to negotiate, but only with the US and not with the Kabul government.
The Taliban has said it will talk to the United States, but not the Western-backed Afghan government the insurgents see as illegitimate.
They have offered to talk directly to the United States about a possible peace agreement.
"It's all working to achieve a political reconciliation, not a military victory", Mattis said.
The Afghan security forces were able to stop some attacks, Mattis said, though he noted he wanted to see them shift to a more "offensive mindset" in the coming months.
The strategy, Mattis said, is to "peel off" those militant elements who may be exhausted of fighting, while continuing to pursue a peace process with the Taliban leadership.
However, Mattis says a diplomatic solution must be between Kabul and the Taliban.
In a report published late on March 12, the UN Office for Coordination of Humanitarian Affairs said that more than 30,000 people have been displaced since the beginning of the year due to continued conflict in Afghanistan.
Stephen Biddle, a George Washington University political science professor and longtime observer of the Afghan conflict, is skeptical that the new USA strategy will make a decisive difference militarily, although he sees "glimmers of hope" for progress toward a peace settlement. These and other moves boosted the number of US troops in Afghanistan by at least 3,500 to a total of more than 14,000.