Pressure mounted on Afghan President Hamid Karzai Sunrday to accept a possible runoff in the country's disputed election as extended diplomacy delayed the announcement of the official results from the August polling.

In Kabul, diplomats and observers said Karzai's supporters have resisted accepting the findings of an inquiry by the UN-backed Electoral Complaints Commission into poll fraud – a key factor behind delays in announcing the outcome.

Under Afghan law, the country's independent election commission has to accept the ECC probe findings, adjust the election tally and announce the final result.

As talks proceeded, observers said pressure was mounting on Karzai to agree to face his main challenger, former foreign minister Abdullah Abdullah, in a second round, or form a power-sharing government.

The Afghan leader has made clear he would prefer not to fight a second round and has spoken out against the investigation, making veiled accusations of foreign meddling.

A host of high-profile visitors were in Kabul over the weekend, including U.S. Secretary of State Hillary Clinton, U.S. Senate Foreign Relations Committee Chairman John Kerry and French Foreign Minister Bernard Kouchner. Kerry said Washington should not proceed with a new Afghan strategy without a clear partner in Kabul.

Preliminary figures gave Karzai 54.6 percent of the vote and Abdullah 28 percent.

While accusing Karzai's camp of fraud and calling for a second round, Abdullah has hinted that he might be open to discussions after the first-round result is announced.

The election is a vital element in Western plans to stabilize Afghanistan and deny sanctuary there to militants believed to have used it as a base for actions across the globe, including the Sept. 11, 2001, attacks on the United States.

More than 100,000 foreign troops are in Afghanistan fighting Taliban insurgents, but growing casualties and doubts about the Karzai government are undermining support for the effort in the United States, Britain and other countries involved.