NATO in Afghanistan spoke out against Pakistan's moves to reach peace deals with Taliban militants on its side of the border as new violence left 16 people dead, including a US-led soldier, the AP reported.
Visiting US congressman also said they were concerned that Islamabad's peace talks with militants could preclude a rise in attacks in Afghanistan, where 70,000 foreign soldiers are helping to fight a Taliban-led insurgency.
NATO spokesman Mark Laity urged Pakistan to avoid agreements that "put our troops and our mission under threat," and said Islamabad must take the alliance into account when it makes such deals.
Top Pakistani militant leader Baitullah Mehsud said at the weekend he would continue "jihad," or holy war, in Afghanistan while pursuing peace talks with the new Pakistan government.
Islamabad has already signed a peace deal with pro-Taliban militants in the Swat Valley, about 99 kilometres ( 55 miles) from Afghanistan.
"They have a sovereign right to make agreements," Laity said at a press conference, adding however, "We have a right to answer if those agreements put our troops and our mission under threat.
"It is no real solution if trouble on one side of the Durand Line (the border) is merely transferred to the other side."
Laity said NATO believed an increase in militant activity along the eastern border with Pakistan could only be attributed to a reduction in the Pakistani army's efforts against militants because of the peace talks.
Afghan defence ministry spokesman General Mohammad Zahir Azimi told the same media briefing that Pakistan territory "should not be used to kill innocent people in Afghanistan."
"Previous peace accords between Pakistan's government and insurgents have shown that it was a golden time for insurgents -- they got equipped, they got ready and they launched operations against both governments," he said.
Azimi appeared to be referring to a now-defunct 2006 peace agreement in Pakistan's North Waziristan area, which led to an increase in suicide bombings and other attacks just across the border in Afghanistan.
Four Democratic lawmakers said after talks with Karzai that they would raise concerns about the peace deals with militants during a visit to Islamabad.
"They are protected in their sanctuaries and yet they come into Afghanistan and take on the activities of terrorists," said one of the lawmakers, Ben Nelson, a US Senator from Nebraska.
The Taliban were removed from government in a US-led invasion in 2001 when they would not hand over Al-Qaeda leaders for the September 11 attacks.
The network has regrouped in Pakistan and a Pentagon report on Friday said the growth of Al-Qaeda safe havens there was "troubling."
A soldier with the US-led coalition and two Afghan policemen were killed Sunday in fresh fighting with Taliban, the coalition and Afghan police said.
A dozen Taliban were also slain in the clashes in the southwestern province of Farah, said police spokesman for western Afghanistan, Abdul Mutalib Rad.
In another incident, a suicide car bomb blew up near NATO troops in the southern city of Kandahar, wounding three soldiers and two Afghan children, Canadian and Afghan officials said.
Last year was the deadliest of the Taliban-led insurgency, with 8,000 people killed, according to UN figures. Most of the dead were rebels, though 1,500 civilians and several hundred soldiers were also slain.