The participation of the Pashtun ethnic group -- from whom the Taliban get most of their support -- is seen as essential to the success of the presidential election, scheduled for April 5.
The vote will be an important test of Afghanistan's progress since the fall of the Taliban regime in 2001. The United States and other foreign donors say the poll is crucial for the country's future after NATO-led combat troops withdraw next year.
"Selection, de facto, takes place in Washington... participation in such elections is only a waste of time, nothing more."
In previous elections, the Taliban called on Afghans to boycott voting, sent fighters to block roads to polling stations and targeted candidates and activists.
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Pashtuns often complain they are unable to vote due to poor security and Taliban threats, pointing to Pashtun-majority Ghazni province where ethnic Hazara candidates won all 11 seats in 2010 parliamentary elections.
Omar offered glimmers of hope for peace after 12 years of fighting, saying that the Taliban -- who sheltered Al-Qaeda during their harsh rule of Afghanistan from 1996-2001 -- did not seek a return to absolute power.
"(The Taliban) does not think of monopolising power," he said. "Rather we believe in reaching understanding with the Afghans regarding an Afghan-inclusive government based on Islamic principles."
Omar's message also said "nor (will) we allow anyone to harm others from our soil" -- a vow in line with US demands that the country does not return to being a safe haven for global militancy.
But Omar, who presided over the Islamist regime, signalled a partial change to their extreme interpretation of sharia law.
"To protect ourselves from scarcity and hardships, our young generations should arm themselves with religious and modern educations because modern education is a fundamental need of every society," he said.
Nearly 70,000 US troops and 30,000 soldiers from other countries are still deployed in Afghanistan, fighting the Taliban and training up the national army and police to take on the insurgents.