Secretary of State Hillary Clinton said Wednesday that negotiations with the Taliban are still possible.
Clinton arrived in Kabul on an unannounced visit late Wednesday night for a meeting with President Hamid Karzai, Radio Free Europe reports.
Insurgents can be part of a peaceful future for Afghanistan or "face continuing assault," Clinton said in a joint news conference with Karzai.
"We are increasing the pressure on the Taliban," Clinton said.
Clinton was scheduled to make her way to Pakistan late Wednesday to meet CIA chief David Petraeus and Chairman of the U.S. Joint Chiefs of Staff General Martin Dempsey.
Insurgents have been completing some high-profile assassinations and assaults on major cities and military targets recently. The Haqqani network, a militant group based on the Durand Line, is thought to be responsible for the attacks.
Relations between the U.S. and Pakistan have strained over the past year with reports surfacing that the Pakistani government withheld information on the whereabouts of Osama Bin Laden.
The U.S. government has also pressed Pakistan to crack down on terrorist organizations in tribal areas.
Clinton said Pakistan has a significant role in combating terrorism.
"Pakistan's cooperation is critical. Violent extremism has also taken the lives of thousands of Pakistanis as well as Afghans and, if you look beyond the history of distrust, it is clear that all countries in the region will have to work together for all the people in the region," Clinton said.
Karzai cut off peace talks with the Taliban when former President Burhanuddin Rabbani was assassinated last month by a suicide bomber.
He also said relations with Pakistan must improve.
"We believe that the Taliban, to a very, very great extent -- to a very, very great extent -- are controlled by establishments in Pakistan, stay in Pakistan, have their headquarters in Pakistan, launch operations from Pakistan," Karzai said.
"Therefore, it is not in a manner of pointing the finger, or in a manner of reprimand that we seek to talk to Pakistan, but in a manner of trying to find the proper venue and the proper authority for talks."
Clinton reassured civic leaders that negotiations with Islamist militants wouldn't hinder progress in areas like women's rights and education.
The U.S. is set to withdraw troops and hand over security to the Afghans by 2014.