US Secretary of State Hillary Clinton has rejected Afghan President Hamid Karzai's claim that officials from the United States and the European Union were responsible for the widespread fraud in last year's presidential elections.

The White House said the remarks were "preposterous" and "troubling".

President Karzai telephone Secretary Clinton to explain his remarks. Officials say Mr Karzai did not specifically apologize during the conversation with Secretary Clinton but expressed "surprise" that his claim that foreigners orchestrated the electoral fraud had caused such a furor.

The row comes just a few days after President Barack Obama made a secret trip to Kabul to press the Afghan president on tackling corruption and to demand progress on good governance.