The United States may refuse a visa to Hamid Karzai's running mate in the election because of his alleged links with the drug trade.
Muhammed Fahim, due to become vice-president if Mr Karzai wins, has been accused by the US Secretary of State Hillary Clinton of being involved in opium trafficking. American officials say this could make it legally impossible to let him enter the US.
The controversy over Mr Fahim, defence minister in Mr Karzai's last government, is yet another sign of rising tension between Washington and the incumbent president.
The Independent revealed this week how Richard Holbrooke, the American envoy to Afghanistan and Pakistan, clashed with Mr Karzai over his choice of electoral allies, such as Mr Fahim and the warlord Abdul Rashid Dostum. He also claimed the president's team had engaged in ballot fraud.
Mr Karzai is said to have walked out of the meeting after 20 minutes after Mr Holbrooke suggested that a second round of voting would be necessary to alleviate public scepticism over the probity of the election. The US envoy subsequently spent three hours in talks with the rival presidential candidate Abdullah Abdullah.
The growing antagonism between Mr Karzai and the West is mutual. The Afghan President is said to have been deeply unhappy at the "patronising" tone taken by Mr Holbrooke and is said to be preparing himself for a lecture by a senior British politician who is due in the country. A supporter of Mr Karzai, who has flown over from America to help with the campaign, said: "It could be useful, perhaps he can tell Afghan MPs how to maximise their expenses."
There is also a future confrontation in the making with Britain after the election over the Helmand governor, Gulab Mangal, who is backed by London. Mr Karzai had in the past planned to replace him with Sher Mohammed Akhunzadi, a former holder of the post, who has been accused of corruption and human rights abuses.
The UK has so far managed to protect Mr Mangal. But another governor favoured by Britain, Engineer Daoud, was removed by the Afghan president who is said to want to reward Mr Akhunzada for delivering votes in Helmand. Similarly, Mr Karzai needs the support of Mr Fahim and General Dostum, with their northern power bases, to counter Dr Abdullah, who is of Tajik and Pashtun descent, and is dependant on voters in the north of the country.
Barack Obama has stated that General Dostum should be investigated for his part in the deaths of thousands of Taliban prisoners after the 2001 war. However, it is the position of Mr Fahim which poses the biggest problem for the United States.
The former Northern Alliance commander was intimately involved with the CIA in the campaign against the Taliban, and became defence minister when Mr Karzai came to power. But reports began to circulate that he was using his position in his capacity as an opium poppy trafficker and the State Department at one point warned the Pentagon that it may be illegal to channel military aid through him. However, the warning was ignored and Mr Fahim continued to meet senior US officials such as the then Defence Secretary Donald Rumsfeld and Lt-Gen Karl Eckenberry in charge of military assistance to the new Afghan army.
However the Obama administration has deliberately taken a tougher stance towards Mr Karzai compared to that adopted by the White House under George W Bush. The new US position makes little secret of its displeasure at the Afghan leader surrounding himself with figures with tainted reputations including his brother, Walid, who is accused of being involved in the drug trade.
One US official said: "It was difficult enough with Fahim being defence minister, but it would be even more problematic if and when he becomes vice-president. We'll have a situation of American soldiers fighting, and dying, for a country whose second most powerful man is a narco-suspect. There are government reports accusing him of trafficking. How can you let such a man into the States? He can end up facing charges."
Supporters of Mr Karzai insist that the allegations against Mr Fahim and Walid Karzai are politically motivated. They also complain that Western officials and the media have concentrated on malpractices by the Karzai camp in the election when there has been widespread voting fraud in the northern region by Dr Abdullah's team.
This was backed by another candidate, Ramzan Bashardost, who commented: "Let us not kid ourselves, Abdullah Abdullah's people were also involved in illegal activities, it just happened in a different part of the country."
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