President Karzai pledged during the live debate on Sunday to rein in the operations of international forces in the country.
Karzai, considered the election frontrunner, took to the stage with Ramazan Bashardost, an independent candidate, and Ashraf Ghani, the former finance minister.
Abdullah Abdullah, the former foreign minister, pulled out of the debate, which was aired on state broadcaster Radio and Television Afghanistan (RTA), an announcer said.
James Bays, Al Jazeera's correspondent based in Afghanistan, said: "If Karzai is re-elected, he said he was going to make some big changes and the most significant points concerned foreign forces.
"He said that there will be no military operations by international forces if they were not first permitted by Afghans.
"He said he would not allow international forces to search Afghan homes. And he said he didn't want any Afghans in the future to be held in jails run by foreigners.
"So that means that controversial prison base at Baghram airport - which lots of human rights organisations have been talking about - will have to close."
Abdul Rashid Dostum, an exiled Uzbek leader, whose supporters could swing the presidential election, returned to Afghanistan also on Sunday after being given a government all-clear.
Dostum's supporters, who gave him 10 per cent of the vote in the 2004 election, had threatened to withdraw their backing for Karzai on August 20 unless the former communist general was allowed to return.
Aminullah Habibi a research fellow at the British Defence academy, who fled Afghanistan in the late 1990s, told Al Jazeera: "Afghanistan is ethnically a divided society; politics is defined on the line of ethnicity.
"You cannot ignore [Dostum's supporters]."
The latest military deaths, which take the UK toll to 204, came after the Taliban dropped leaflets threatening to cut off voters' fingers and attack polling stations in its bid to force Afghans to boycott the presidential elections.
One of the so-called "night letters", left on the ground in villages in southern Afghanistan, threatened that the Taliban would cut off the noses and ears of those who vote on Thursday.
|The Taliban warned that they would cut off the noses and ears of those who go to vote [AFP]
Qari Yousuf Ahmadi, a Taliban spokesman, confirmed that commanders were ordering a boycott of the vote.
"We are using new tactics targeting election centres ... We will accelerate our activities on election day and the day before," he said.
The threats came as hospital sources in Kandahar said one person was killed and another eight injured on Sunday after three mortars were fired into the centre of the city.
The attack happened not far from a pro-Karzai rally in the city's main sports stadium.
Another eight people were killed in a suicide attack, just outside the headquarters of Nato's International Security Assistance Force (Isaf) in the Afghan capital on Saturday.
Opinion surveys have shown Karzai may not win the election by enough votes to avoid a run-off against his strongest challenger, Abdullah Abdullah.
Campaigning ends at midnight on Monday, before about 17 million people out of Afghanistan's 33 million population eligible to vote, head to the polls.