Taliban have 'not met their commitments' in peace deal: US
Top Taliban negotiator discusses peace talks with Moscow
Kirby said the new administration of President Joe Biden remains committed to the February 2020 peace agreement set in Qatar between the United States and the Afghan insurgent group.
That agreement required the Taliban to halt attacks on US forces, sharply decrease the level of violence in the country, and advance peace talks with the government in Kabul.
In return, the United States would steadily reduce its force level in the country, and remove all forces by May 2021.
Kirby said there is "no change" to the US commitments made in the peace deal. However, he said, "the Taliban are not meeting their commitments to reduce violence, and to renounce their ties to Al-Qaeda."
As long as that remains the case, he said, "it's going to be difficult for anybody at that negotiating table" to stand by their own promises.
"In fact, it would not be the wise course," he added, underling the US commitment to ending the war "in a responsible way."
Kirby said the US Defense Department is comfortable with the current level of 2,500 US troops in the country, down from close to 13,000 a year ago.
It is enough to carry out the main US mission in the country now, to counter the Islamic State and Al-Qaeda forces operating in Afghanistan, he said.
But he would not say if the Pentagon would cut troop levels to zero by the May deadline.
"I would say this to the leaders of the Taliban, that... they make it that much more difficult for final decisions to be made about force presence by their reticence to commit to reasonable, sustainable and credible negotiations at the table," he said.
Taliban negotiator in Moscow
A top Taliban negotiator discussed Afghan peace talks with Russian officials in Moscow on Thursday, the group said, a week after the Biden administration announced it would review Washington's 2020 deal with the insurgents.
Sher Mohammad Abbas Stanekzai, the deputy head of the Taliban negotiating team that is holding peace talks with the Afghan government, met Russian President Vladimir Putin's special envoy for Afghanistan Zamir Kabulov and other foreign ministry officials during the Moscow visit.
"The ongoing situation of the intra-Afghan negotiations and subjects concerning the full implementation of the Doha agreement were discussed during the meeting," Taliban spokesman Mohammad Naeem said on Twitter, referring to the US-Taliban deal signed in the Qatari capital in February 2020.
"Russia assured its support for restoring peace in Afghanistan."
Taliban representatives visited Russia several times before entering into talks with the Trump administration which finally culminated in the landmark February 2020 deal.
This latest visit to Moscow comes just a week after President Joe Biden's administration said it was reviewing that deal, to determine whether the Taliban has reduced attacks in Afghanistan, in keeping with its side of the agreement.
The deal paved the way for the withdrawal of all foreign forces from Afghanistan by May this year -- in return for the insurgents offering some security guarantees and agreeing to hold peace talks with Afghan government.
The peace talks began on September 12 but violence has surged in Afghanistan.
High-profile assassinations have increased in recent months, particularly in Kabul, where several journalists, activists, judges and politicians have been murdered in brazen daylight attacks.
Officials blame the Taliban for the killings, though the group has steadfastly denied any involvement.
During the talks in Moscow on Thursday, the Russian side "spoke in favour of the early launch of meaningful and constructive inter-Afghan negotiations, leading to an end to the bloody civil war," the Russian foreign ministry said in a statement.
Despite months of discussions, the peace talks between the Taliban and Afghan government in Doha have largely stalled, according to Kabul's negotiating team.