In his Eid-ul-Fitr message, Hekmatyar said those who expected that the peace process would yield a solution to the crisis in Afghanistan were lying.
"The only solution is to continue the jihad until all the foreign forces fully leave Afghanistan," he said in a statement issued yesterday.
Hekmatyar's Hizb-e-Islami had been involved in talks with the Afghan government and US officials, but the parleys were suspended after Kabul signed a strategic partnership agreement with Washington earlier this year.
The Taliban too were involved in talks with the US over the past two years but the process has now been suspended in the wake of differences over certain issues, including the release of prisoners.
"Those who think that the war will end in the presence of foreign military are wrong," said Hekmatyar, who has been in hiding for years.
He said peace and security could only be restored if foreign forces withdraw from Afghanistan.
Not only are the mujahideen strong, but the cost of the war, which was USD 120 billion annually, was taking its toll on the US economy, he claimed.
He went on to praise Afghan fighters for launching attacks during Ramzan, which were the highest in number in the past 11 years.
"This long war has pushed the US and its allies to serious financial and political crises. They have not achieved anything and are biting everyone like a wounded snake," Hekmatyar said.