World leaders have welcomed the acceptance by Afghanistan's President Hamid Karzai of the decision to hold a run-off presidential election.

世界各国领导纷纷对阿富汗总统Hamid Karzai决定进行一次关键性总统选举的做法表示肯定。

The move came after weeks of international pressure

US President Barack Obama described the second round, due on 7 November, as a "constructive¹" step forward.

British Prime Minister Gordon Brown also welcomed the "statesmanlike" move.

It came a day after a UN-backed panel said it had clear evidence of fraud in August's first round, lowering Mr Karzai's vote share below 50%.

Mr Karzai - who will compete against his closest rival, Abdullah Abdullah - told a news conference that it was "the time to move forward to stability and national unity²".

Mr Abdullah, speaking to the BBC, said the move would "help democracy in this country and strengthen the faith of the people in the democratic process".

'Huge challenge'

Since the disputed first round of polling, there has been intensive Western lobbying（游说） of Afghanistan's leaders to resolve the weeks of political paralysis³（瘫痪）.

The White House - debating a request for 40,000 more US troops to be sent to Afghanistan - warned at the weekend that no more soldiers would be deployed⁴（配置，部署） until a political resolution was reached.

Mr Obama welcomed news of the run-off, saying: "It is now vital that all elements of Afghan society continue to come together to advance democracy, peace and justice."

UN Secretary General Ban Ki-moon commended President Karzai "for the leadership he has displayed".

But he warned of the "huge challenge in conducting（指挥，引导） a second election".

"We will try to ensure that all Afghan people should be able to express their own will freely without intimidation⁵（恐吓，威胁） or threat," he said.

French President Nicolas Sarkozy said: "President Karzai's statement shows to all that he is a statesman who can decide on what is essential, in the higher interests of his country and of the unity of the Afghan people."

'Strengthen our resolve'

Initial election results suggested Mr Karzai, the incumbent⁶, had received 55% of the vote, and ex-Foreign Minister Mr Abdullah 28%.

But on Monday the UN-backed Electoral Complaints Commission (ECC) ordered that ballots⁷ from 210 polling stations be discounted.

This meant Mr Karzai's total was reduced to below the 50% threshold（极限，门槛） for outright⁸ victory, indicating a second round was needed.

Mr Karzai gave his reaction to the run-off at a news conference on Tuesday, alongside UN envoy⁹ Kai Eide and US Senator John Kerry.

"I call upon our nation to change this into an opportunity to strengthen our resolve and determination, to move our country forward and to participate in the new round of elections," he said.

Mr Abdullah told the BBC he had telephoned Mr Karzai to thank him for his remarks.

"He talked about national unity and also he stressed on the need for going to the second round which is exactly what I want to do - so that was a courtesy call（礼节性访问，拜会）, a word of thanks," he said.

Mr Abdullah added: "I know that there are challenges with it; the security situation, and the winter is coming...

"But I think the fact that the process is moving now forward rather than being stuck, that in itself I consider it a step forward and we have to face the challenges."

The BBC's Martin Patience in Kabul says there will be no guarantee that any new vote will be free of the fraud that dogged the first round.

But for now the political deadlock¹⁰（僵局，停顿） appears to have been broken, for a couple of weeks at least, our correspondent says.

Mr Kerry said a second round of voting was a great opportunity and a turning point, praising Mr Karzai for the "genuine leadership in the decision he has made".

Meanwhile, correspondents say it is possible that President Karzai and his challenger may reach an agreement to form a national unity government, meaning that a run off may not be required.