Ecuador has announced it is expelling the US ambassador in Quito.
The move follows the release on Monday by the whistle-blowing website Wikileaks of a US diplomatic cable alleging widespread corruption within the Ecuadorean police force.
Foreign Minister Ricardo Patino said he had asked Ambassador Heather Hodges to leave the country as soon as possible.
The US state department called the decision "unjustified" and said it deeply regretted it.
'Irresponsible and false'
Mr Patino said that after the release he had called Ambassador Hodges to ask how the US had "had access to such restricted information".
Asked if he thought that the US had infiltrated the Ecuadorean police force, he answered "it would be nothing new".
He told reporters at a news conference the decision to expel the US ambassador had been taken after she failed to give a satisfactory explanation to accusations she had made in the diplomatic cable revealed by Wikileaks.
He said the move was not aimed at the United States in general but only against one official who had made serious allegations against Ecuador.
In the cable, the ambassador suggests Ecuadorean President Rafael Correa was aware of corruption allegations against senior policeman Gen Jaime Aquilino Hurtado Vaca when he made him commander of the country's police force.
Mr Patino said the accusation against President Correa was "absolutely irresponsible and false".
Gen Hurtado Vaca served as commander of the Ecuadorean police force for just over a year before his resignation in June 2009.
The diplomatic cable says the US Embassy had "multiple reports that indicate he used his positions to extort bribes, facilitate human trafficking, misappropriate public funds, obstruct investigations and prosecutions of corrupt colleagues, and engage in other corrupt acts for personal enrichment."
Gen Hurtado Vaca has denied the allegations.