Ban Ki Moon, the UN Secretary-General, flew into Kabul this morning to discuss security for his staff and help broker a power-sharing deal between President Karzai and Dr Abdullah Abullah following the latter’s withdrawal from a presidential election run-off.

Mr Ban is expected to meet security officials to discuss the safety of roughly his 6,000 employees in Afghanistan following a Taleban suicide attack on a UN guesthouse last week in which five foreign UN staff were killed.

The UN has criticized Afghan and Nato forces for not responding quicker to the attack, and has asked the UN General Assembly and Security Council to provide more security for its staff, who it says have become “soft targets” for the Taleban.

Mr Ban will also meet Mr Karzai and Dr Abdullah as part of international efforts to broker a power-sharing deal that would allow the cancellation of an election run-off on Saturday, and finally resolve Afghanistan’s two month election crisis.

A deal would also allow President Obama to decide, most likely in the next few days, whether he has a credible enough partner in government to send up to 80,000 more US troops to Afghanistan as part of a new counter-insurgency strategy.

Dr Abdullah withdrew from the run-off yesterday in protest at the government’s failure to combat election fraud, effectively handing Mr Karzai a second term, but also threatening to undermine the legitimacy of the new government.

Mr Ban would “assure them and the Afghan people of the continuing support of the United Nations towards the development of the country and the humanitarian assistance that the UN provides to millions of Afghans everyday”, the UN said in a statement.

The UN has told almost all its foreign staff not involved directly in the elections to leave Afghanistan temporarily, but has stopped short of ordering a full evacuation, as it did from Iraq after a truck bomb killed 22 people at its headquarters in Baghdad in 2003

Diplomats said that the UN and the US were leading efforts to persuade Mr Karzai's camp to cancel the run-off, on the grounds that turnout would be very low and the risk of further fraud and more Taleban attacks very high.

The Independent Election Commission, which is organising the election, is still saying the run-off must go ahead as ballot papers have been printed and there is no other constitutional way to choose a president.

Western officials say a better option would be to ask the Supreme Court to make a ruling on the issue.

They are also trying to help negotiate a deal under which Mr Karzai and Dr Abdullah would divide up ministries, provincial governorships and other influential positions between their powerful allies and financial backers.

They had almost reached a deal yesterday, before Dr Abdullah’s announcement, but the talks fell through at the last minute, according to diplomats.

The US and its allies have now accepted that Mr Karzai will remain as President, but are trying to ensure that his next government is inclusive enough to be a credible partner in the fight against the Taleban, diplomats say.

"There's a resignation that Karzai is the player we are going to have to deal with, but he is being told in no uncertain terms, that he is a wounded animal,” one senior Western official told The Times.

“In the eyes of the Afghan people and in the eyes of the international community he has to rebuild his credibility. The first test will be his cabinet. If we see thugs, criminals and drug dealers in the cabinet, international support will wither."

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