Security has been stepped up across the country ahead of the poll Voters in Afghanistan are due to cast their ballots in key parliamentary elections, despite fears of violence and threats from Taliban militants.
More than 2,500 candidates are vying for 249 seats in the lower house of parliament, the Wolesi Jirga.
Some 280,000 soldiers and police are being deployed around the country.
The poll is seen as a test of credibility for Mr Karzai after last year’s presidential elections, which were marred by widespread fraud.
Mr Karzai – under strong diplomatic pressure – eventually accepted that irregularities had occurred but his main rival, Abdullah Abdullah, withdrew from a run-off saying the vote could not be free or fair.
Washington is watching Saturday’s poll closely, as US President Barack Obama prepares a war strategy review in December that is expected to consider the scale of plans to start withdrawing American troops from next year.
Nearly 6,000 polling stations in 34 provinces are due to open at 0700 local time (0230 GMT) and will close at 1600 local time (1130 GMT). But about 1,000 will not open because of security fears.
Date of voting: 18 SeptemberNumber of eligible voters: about 10.5 millionNumber of seats: 249Total number of candidates: 2,514, including 406 womenTotal number of polling centres: 6,835Polling centres closed because of security concerns: 1,019Estimated cost: $150m (£95.5m), paid by international partnersQ&A: Afghan elections
There are more than 10 million registered voters, but the UN says a turnout of five to seven million would be a success, given the difficulty of holding a poll in the middle of a war.
Afghan soldiers and army will be guarding the polls, backed up by nearly 150,000 foreign troops.
Ahead of the vote, President Karzai urged Afghans to cast their ballots, despite threats from the Taliban to attack voters and election officials.
“Tomorrow’s election is very important. I hope all our people in all corners of the country, in any village will go to the polling centres and to vote for their favourite candidate,” Mr Karzai told reporters on Friday.
The Taliban have warned voters to boycott the poll and “stick to jihad”.
In what correspondents say is a thinly veiled threat, the insurgents have said in a statement that they have “already chalked out certain measures… to frustrate this American process and will implement them on the day when the illegitimate process of elections is conducted”.
The Taliban has already claimed responsibility for kidnapping two parliamentary candidates and 18 poll officials and campaign workers in separate incidents in the run-up to the elections.
Another major concern for Afghan election officials and international observers is that the polls will not be free or fair.
Mr Karzai on Friday admitted that “under the circumstances we must expect that there’ll be irregularities, there’ll be problems and there’ll be allegations as well”.
The UN special envoy to Afghanistan, Staffan de Mistura, also acknowledged earlier this week that the elections “will not be perfect”.
On Tuesday, officials from Afghanistan’s Independent Election Commission (IEC) said 3,000 forged voter registration cards had been confiscated in the central province on Ghazni.
However, IEC officials stressed that they had taken a number of measures – including the usage of an indelible ink to avoid double voting – to prevent fraud.
Preliminary results are to be announced on 22 September, with the final results due on 31 October.
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