US allies Mexico, Brazil, Colombia and Chile have joined other Latin American nations in demanding answers from Washington over spying allegations.
Brazilian media reported earlier this week that the US had seized web traffic and phone calls across the region.
Spying targets included oil and energy firms, Venezuela's military purchases and information on Mexico's drug wars.
The reports, based on leaks by fugitive Edward Snowden, said the US ran a "data-collection base" in Brasilia.
The O Globo newspaper said the US facility in the Brazilian capital was part of a network of 16 such bases maintained by the National Security Agency (NSA) around the world to intercept transmissions from foreign satellites.
The paper said it had evidence that the base was in operation until at least 2002, but it was unclear whether it still existed.
Brazil apparently remains the main target of US snooping in Latin America, with major firms and foreign visitors routinely targeted.
The surveillance was allegedly conducted through partnerships between Brazilian telecoms firms and US agencies, although the reports did not name any companies.
On Monday Brazilian President Dilma Rousseff urged the US to explain, and has ordered an investigation into the claims.
She said if true they would represent "violations of sovereignty and human rights".
During angry exchanges in parliament on Wednesday, senators suggested Brazil should give Mr Snowden asylum, while others said Brazil should cancel lucrative defence contracts with the US.
The allegations on O Globo detailed claims of US spying across Latin America, sparking an angry reaction from traditional American foes in the region like Venezuela and Ecuador.
But analysts say the US will be much more concerned with the irritation the revelations have caused in Brazil, Colombia, Mexico and Chile.
Mexican President Enrique Pena Nieto said the foreign ministry had asked "quite clearly" for an explanation about the spying allegations.
"And we want to know if this is the case, and if it is so, it would obviously be totally unacceptable," he said.
Officials in Chile and Colombia made similar statements earlier in the week.
Mr Snowden is still believed to be staying in the transit area of Moscow's Sheremetyevo airport, where he fled after being named as the source of a series of leaks about the US spying programme.
He has asked for asylum in several countries, with Bolivia, Nicaragua and Venezuela indicating they would offer him refuge.
According to various reports, Venezuela appears his most likely destination, although it is unclear how he can get there without being intercepted by the US or its allies.
Mr Snowden's leaks have led to revelations that the US is systematically seizing vast amounts of phone and web data across the world, under an NSA programme known as Prism.