The Taliban suspended the talks one year ago, blaming "shaky, erratic and vague" US statements.
The US government has said it remained committed to political reconciliation involving talks with the Taliban but progress would require agreement between the Afghan government and the insurgents.
"Senior leaders of the Taliban and the Americans are engaged in talks in the Gulf state on a daily basis," Karzai told a gathering to mark International Women's Day.
But the Taliban spokesman in Afghanistan, Zabihullah Mujahid, denied that negotiations with the United States had resumed and said no progress had been made since they were suspended.
"The Taliban strongly rejects Karzai's comments," he said.
US officials could not be immediately reached for comment.
The Kabul government has been pushing hard to get the Taliban to the negotiating table before most US led Nato combat troops withdraw by the end of 2014.
Afghan officials have not held direct talks with the militants, who were toppled in 2001 and have proven resilient after more than a decade of war with Western forces.
US diplomats have been seeking to broaden exploratory talks with the Taliban that began clandestinely in Germany in late 2010 after the Taliban offered to open a representative office in Qatar.
US Defense Secretary Chuck Hagel is in Afghanistan to visit US troops.
Hagel, who arrived on Friday for his first trip abroad as defense secretary, is also due to hold talks with Karzai, whose recent orders to curtail US military activity highlights an often tense relationship with the 66,000 American forces here.
Hagel's visit also coincides with the passing of a deadline imposed by Karzai for US special forces to leave the province of Wardak, after Karzai accused them of overseeing torture and killings in the area.
US forces have denied involvement in any abuses and it was not clear if they were leaving Wardak by the deadline.
Regional power Pakistan indicated a few moths ago that it would support the peace process by releasing Afghan Taliban detainees who may help promote the peace process.
But there have been no tangible signs the move advanced reconciliation.
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