Afghans are due to go to the polls on June 14 to choose whether Ashraf Ghani or Abdullah Abdullah should succeed President Hamid Karzai.
The militants, ousted from power in Kabul by a 2001 US-led invasion, threatened to attack the first round of voting on April 5 but the day passed off with no major security incidents.
In a statement in English on their website, the Taliban said their fighters "are once again fully prepared to operate against the workers and polling stations in the second phase of these counterfeit elections".
"Therefore, you (the masses) should remain far away from the polling stations on 14th June, 2014, lest you should be hurt or killed."
On Friday Ghani, a former World Bank economist, said if elected he would put his name to a long-delayed security pact with the United States that Karzai has refused to sign. Abdullah has also said he would sign.
Ghani's pledge came only days after US President Barack Obama said the 32,000 American forces in Afghanistan will be scaled back to 9,800 by early 2015 and complete a full withdrawal by the end of 2016.
Ghani faces an uphill task after finishing second with 31.6 per cent -- behind Abdullah with 45 percent -- in the eight-candidate first round.
The Taliban last week denounced US plans to keep troops in Afghanistan until the end of 2016, threatening to wage war against the "occupation" until the very last foreign soldier pulls out.