"That's when we learned of all this, of the military group, nearly 50 military personnel. This is inconceivable," he told foreign reporters.
"Unfortunately, these people have been so infiltrated in all the sectors that what is scandalous appeared normal."
Correa, an economist by training who has long railed against America's "imperialism" in its Latin American backyard, said Quito was "already taking measures" to address the issue.
US Embassy spokesman Jeffrey Weinshenker said the United States had not yet received "formal notification" of the Ecuadoran request.
He said about 20 US Defense Department employees, both military and civilian, were assigned to the embassy and were "fully accredited."
"All our activities are carried out with the explicit approval of the Ecuadoran counterparts," he said.
In Washington, a US official also said that the 50 military personnel cited by Correa were "more than double the actual number.
Correa has been often at odds with the United States since first taking office in 2007.
"We want it to be better, but let's not fool ourselves: yes, there are certain tensions, there is mutual distrust," the president said, pointing to Washington's "goofy" policy toward governments it considers hostile.
"It's not that we are anti-American, but we will always denounce double standards in international policy, and if that strains our relations with America, we will never renounce our principles."
The United States is Ecuador's main trading partner, and has repeatedly questioned Quito's links with Iran and Belarus, its decision to grant asylum to WikiLeaks founder Julian Assange and Correa's troubled relationship with the press.