A former national security adviser has registered as a candidate for president of Afghanistan and called on the Taliban to engage in peace negotiations to end the country's 17-year war.

Mohammad Hanif Atmar, of the Peace and Moderation party, announced his candidacy on Friday in an address to hundreds of supporters at a hotel in Kabul.

Afghans go to the polls to elect a new president on July 20.

Current Afghan president Mohammad Ashraf Ghani says he will register to run for re-election in the coming two days.

The Taliban have been steadfast in their refusal to enter peace talks with the Afghan government and have also threatened to halt talks with the United States.