The United States warned Saturday that it could call on the Taliban to close an office in Qatar unless it shows more commitment to reconciliation in Afghanistan.
US special envoy James Dobbins arrived in the Gulf Arab monarchy and was taking part in talks with Qatar alongside Secretary of State John Kerry.
But Kerry said that the United States was not yet ready to meet the Taliban and accused the rebels of failing to live up to their side of peace efforts.
"It is our hope that this could ultimately be an important step in reconciliation if it's possible. We know that it may well not be possible," Kerry told reporters in Doha.
If the Taliban do not address concerns, "We may have to consider whether or not the office has to be closed."
"It is really up to the Taliban to make that choice," he said, calling a feud in the past week "the first real test of whether the Taliban are prepared to do their part".
The rebels opened the mission in Doha on Tuesday under the name the "Islamic Emirate of Afghanistan", and raised the white Taliban flag.
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Afghan President Hamid Karzai angrily opposed the office, seeing the symbolism as representing a government-in-exile for the Taliban, which imposed an austere brand of Islam when it held sway in Kabul from 1996 until its ouster after the September 11, 2001 attacks on the United States.
President Barack Obama's administration has supported dialogue with the Taliban as the United States prepares to pull out its 68,000 combat troops from Afghanistan next year, ending the longest-ever US war which has become increasingly unpopular at home.
On Saturday, Karzai met lawmakers and again insisted that the peace process should be led by Afghans.
"Peace is a sacred hope for our people. We will continue our efforts for peace and will not allow foreigners to use our peace process for their own ominous ends," a presidency statement quoted him as saying.
Kerry said it was too early to look at Taliban demands such as the release of prisoners.
US officials said that Dobbins, the US special envoy on Afghanistan and Pakistan, would lead any potential talks with the Taliban and that Kerry would not participate.
Kerry was taking part in talks in Doha for the so-called "Friends of Syria" meeting looking at support for rebels fighting against President Bashar al-Assad.
The top US diplomat repeatedly praised Qatar, which has played a growing regional role, for hosting the office.