The United Nation's top envoy for Afghanistan has said that violence is threatening security in the run-up to September's elections.
US-led coalition forces are fighting alongside Afghan troops
Jean Arnault said that rebels loyal to the former Taleban had become more violent.
His comments came as the Afghan and US-led forces ended a big military operation in southern Afghanistan.
Afghanistan has seen some of its worst bloodshed in recent months, with a spate of attacks blamed on the Taleban.
Mr Arnault told the UN Security Council that Afghanistan's national security was going through a "negative evolution".
"The country is confronted with an escalation of both the number and gravity of incidents that affect several provinces," he said.
"The situation is especially worrying in the southern provinces... and in Pashtun regions bordering with Pakistan."
Mr Arnault said that the Afghan and Pakistani governments should reverse the tide of instability.
US and Afghan forces wound up a bloody offensive in southern Afghanistan on Saturday.
Afghan officials say more than 100 Taleban fighters were killed in Zabul province in what was one of the biggest operations for two years.
But the forces failed to find the Taleban leaders they hoped had been surrounded.
Correspondents say that barely a day goes by now without serious violence across south and east Afghanistan.
The US has about 18,000 troops in Afghanistan tackling remnants of the Taleban regime that was ousted in late 2001.
Nearly 400 people have been killed in Taleban-linked violence this year, following a lull during the winter - most of them suspected militants.