KABUL (Reuters) -- Exiled Uzbek leader General Abdul Rashid Dostum, whose supporters could swing this week's presidential election, returned to Afghanistan on August 16 after being given a government all-clear.
Dostum's supporters, who gave him 10 percent of the vote in the 2004 election, had threatened to withdraw their backing for President Hamid Karzai on August 20 unless the former communist general was allowed to return.
The United States made clear its concern over any prospective role for Dostum, a controversial figure associated in the past with factional infighting and accused by human rights groups of abuses.
Surveys show Karzai in the lead but not by enough to avoid a run-off against his strongest challenger, former Foreign Minister Abdullah Abdullah. Campaigning ends at midnight on August 17, three days before the August 20 vote.
Supporters of the main candidates came out in the thousands on August 16 in a last burst of campaigning zeal.
For Western countries, which now have more than 100,000 troops in Afghanistan, the result of the vote may be less important than ensuring it takes place at all. Taliban fighters, stronger than ever since they were driven from power eight years ago, have said they will disrupt the poll.
The vote is also a test for U.S. President Barack Obama, who has declared Afghanistan his administration's main foreign focus. More than 30,000 extra U.S. troops have arrived in Afghanistan this year as part of an escalation strategy.
The U.S. reinforcements have launched the war's biggest offensives, alongside British troops who since last month have suffered their worst battlefield casualties in a generation.
Karzai must secure more than 50 percent of the vote or face a run-off against the next best of 35 challengers. A second round could see his opponents unite behind a single contender. Two U.S.-government funded polls have him at around 45 percent.
Dostum, a veteran politician renowned as a kingmaker, has been in Turkey since last year when the Afghan government released him from house arrest imposed for fighting with a rival.
It was never made clear if Dostum's exile was ordered or self-imposed but on August 16 a government statement said there was no legal reason to prevent him returning.
A U.S. official at the Kabul embassy condemned Dostum's return and said they were concerned at the timing.
"We have made clear to the government of Afghanistan, our serious concerns about the prospective role of Mr. Dostum in today's Afghanistan and particularly during these historic elections," the official said.
"The issues surrounding him become all the more acute with his return to Afghanistan during this period."
Dostum was a key part of the alliance that toppled the Taliban in 2001, but has been accused by human rights groups of widespread abuse, including allowing the massacre of several thousand prisoners during his watch.
The Taliban, now at their strongest since then, rebuffed the August 16 government announcement to observe an "offensive ceasefire" on voting day and said anyone involved in the election put their lives at risk.
"In order for them to not get hurt, we are saying to them to not go to the polling stations or close to the Afghan and foreign forces, for we will carry out suicide attacks or even direct attacks against them," a spokesman told Reuters by satellite phone from an undisclosed location.
Afghan Defence Minister Abdul Rahim Wardak, at a news conference a day after a suicide attack outside the main NATO base in Kabul, acknowledged security forces faced enormous challenges on voting day.
Preparations were boosted by news that the Afghan flag was hoisted for the first time in years over the formerly Taliban-held southern district of Nawzad after being re-taken by U.S. Marines and Afghan forces.
The district centre, in the mountains of Helmand, is all but destroyed after years of fighting -- first by British forces and more recently by U.S. Marines -- against Taliban fighters. The Taliban now hold eight of the country's 356 districts.
The operation in Nawzad follows last month's Operation Strike of the Sword, the biggest of the war, in which 4,000 U.S. Marines swooped in a single night into three districts in the southern Helmand River valley.
British troops launched a huge operation, Panther's Claw, in a separate part of the province, a couple of weeks earlier, but they have suffered Britain's heaviest ground combat casualties since the Falklands War in 1982.
With a ban on campaigning coming into effect 48 hours before polls open, supporters of the main candidates came out in their thousands on August 16.
Karzai disappointed his supporters in his hometown Kandahar, who were hoping he would make an appearance at a rally addressed by one of his half-brothers, Ahmad Wali Karzai, the provincial council chief. Kandahar is also the heartland of the Taliban.
In his own power base in the north, former Foreign Minister Abdullah Abdullah was mobbed by supporters who stormed a gate to surge into the compound where his helicopter touched down.
There are also fears that fraud could jeopardize the legitimacy of the vote, making violence worse. Abdullah played down concerns that his followers could respond with unrest if they feel they have been denied a victory.
"In the unlikely event that Karzai wins, I will encourage sensibility...but this is unlikely because I have already won," he told Reuters.