The US state department called the expulsion unjustified and said it would "respond as appropriate".
"We regret this decision by the government of Ecuador. We also reject any suggestion of wrongdoing by embassy staff," said Gordon Duguid, a state department spokesman.
"Despite the government of Ecuador's unjustified action, we remain committed to working collaboratively with Ecuador to confront narcotics trafficking."
Correa previously ordered the expulsion of Armando Astorga, the US immigration and customs enforcement attache, saying the official had ended a financing deal with local police after authorities refused to abide by his terms in selecting officers in charge of aid projects.
The Ecuadorean leader said Astorga had suspended $340,000 in annual aid to Ecuador's anti-contraband police and had demanded in a January 8 letter that the police return all vehicles, furniture, cameras and phones donated by Washington.
Correa, who enjoys a 70 per cent popularity rating, is running for a second four-year term as president in elections to be held in April.
Hugo Chavez, the Venezuelan president, last year expelled the US ambassador to Caracas and Evo Morales, the Bolivian president, also ordered the US envoy to leave last September after accusing him of fanning civil unrest.