International support for Karzai, who was once the darling of the West, has waned pectacularly, amid worsening violence, endemic corruption and weak leadership. But until very recently, diplomats insisted there were no viable alternatives even as fighting has intensified and the Taliban [Images] insurgency in the south has grown.

But four key figures believed to be rivals of Karzai have arrived in Washington for meetings with Obama administration officials this week, the paper said.

There is now talk of a dream ticket, that would see the main challengers run together to unite the country's various ethnic groups and wrest control away from Karzai.

"The Americans aren't going to determine the outcome of the election, but they could suggest to people to put their differences aside and form a dream ticket," said a senior United States analyst in Kabul told the Independent.

Obama has already started getting to grips with the challenge of Afghanistan; he received a briefing on the coming American troop surge from general David Petraeus on Wednesday, his first full day in the Oval Office.

On Thursday night, Obama appointed the veteran US diplomat, Richard Holbrooke, as his new special envoy for Afghanistan and Pakistan.

The unofficial delegation to Washington was made up of three ex-ministers and a serving governor.

Dr Abdullah Abdullah was the foreign minister, Dr Ashraf Ghani served as finance minister, Ali Ahmad Jalali was interior minister and Gul Agha Sherzai is the governor of the eastern province of Nangahar, where US troops are based.

When Obama visited Afghanistan in July he met governor Sherzai in Jalalabad, even before he met President Karzai in Kabul.

"They are not going to blindly back President Karzai like the Bush administration did for so long," said John Dempsey, head of the United States Institute of Peace in Kabul, told the paper.