EU Special Envoy for Afghanistan Tomas Niklasson issued the warning during an interview with Dawn at the end of his visit to Islamabad on Wednesday.
The diplomat underlined the urgent need for the warring parties to make progress in their peace negotiations in Doha.
He said: “We could, unfortunately, see an increased level of violence over the next few weeks and months.”
With Doha negotiations virtually stalled, insurgent-linked violence has been on the rise in Afghanistan amid the pullout of foreign troops.
The Taliban had not floated any proposal on how they would like to see future governance or a list of subjects they would like to discuss, the envoy said.
The warring sides reportedly conferred on the recalibration of order and sequence of sessions in their meeting on Tuesday.
In talks with both sides, the envoy said, that EU had underscored the urgency to move forward. “We need to move from process to substance.”
He asked the Taliban to demonstrate their sincerity about the peace process. He reminded the militant movement of its promise not to take Kabul by force and that they were committed to a negotiated settlement.
The diplomat urged the Taliban to reduce violence and prove their interest in cooperating with the European Union and others.
Asked about Pakistan’s role in the process, Niklasson said he had noticed a sense of urgency among the Pakistani leaders.