Mullah Omar's message ahead of Eid came a week after President Hamid Karzai reached out to the Taliban during his inauguration speech, saying it was important to include in the government former Taliban who were ready to renounce terrorism.
The extremist group quickly rejected the appeal, repeating its refusal to negotiate with the Karzai government or participate in what it considers a puppet administration.
"I hope you will continue your legitimate jihad (holy war) and struggle in the way of realizing your Islamic aspirations ... and break off all relations with the stooge Kabul administration," Omar said in the message posted on a Web site used by the Taliban and e-mailed to journalists from an address often used to send out his statements.
He said there would be no negotiations that would prolong or legitimize the presence of foreign forces in the country.
"Those who have occupied our country and taken our people as hostage, want to use the stratagem of negotiation like they used the drama of elections for some time in order to achieve their colonialist objectives," he said. "However, the people of Afghanistan will not agree to negotiation which prolongs and legitimizes the invaders' military presence."
Omar hasn't been seen in years. Afghan officials claim he is in hiding in Pakistan.
The Taliban leader insisted the insurgents had gained the upper hand and were winning the war."Ground realities in our beloved country indicate that the invaders are about to escape," he said.
President Barack Obama has been considering plans to send tens of thousands more U.S. troops to Afghanistan, and U.S. military officials expect an infusion of approximately 32,000 to 35,000 troops to begin in February or March. It would be the largest expansion since the beginning of the war in 2001.
In his statement, Omar called on militants to continue to fight against the government and its allies, but urged them to avoid civilian deaths. Taliban bombs often kill civilians in their pursuit of government or military targets.
Militants were to blame for about three-quarters of the 1,500 civilian deaths in the first eight months of 2009, according to the United Nations. However, the Taliban statement blamed U.S. and NATO forces for killing civilians in military operations, and said these nations are guilty of human rights abuses because of the mistreatment of prisoners.
The statement also repeated Taliban rhetoric claiming that the war in Afghanistan is an attempt by the West to undermine Islam.
"The Americans and its allies have been hammering out plans overtly and covertly to destabilize the Islamic world and provoke differences in the Islamic countries," Omar said.