Venezuela has made a formal complaint to the US authorities and the United Nations after its foreign minister was detained at a New York airport.
Mr Maduro says his detention was a breach of international law
The US state department has apologised to Nicolas Maduro who was detained for 90 minutes at New York's JFK airport as he travelled home.
He had been attending this week's UN General Assembly meeting.
He said he was verbally abused and strip-searched in what he said was a "flagrant breach of international law".
President Hugo Chavez described Mr Maduro's detention as a provocation.
Our correspondent Pascale Harter says the apology has done little to ease the tense relations between the two countries.
Mr Maduro said the US apology was not enough.
"We were detained during an hour and a half, threatened by police with being beaten," he told reporters at Venezuela's mission to the UN. "We hold the US government responsible."
US authorities initially denied Mr Maduro had been detained and his documents seized, saying he had simply been asked to go through a second security screening.
The US state department later confirmed the incident had taken place and apologised.
"The state department can confirm there was an incident with Venezuelan Foreign Minister Nicolas Maduro at JFK airport in New York," a spokesman said.
"The state department regrets this incident. The United States government apologised to Foreign Minister Maduro and the Venezuelan government."
President Chavez earlier said Mr Maduro had been questioned about his alleged role in a failed Venezuelan coup attempt in 1992, led by Mr Chavez.
US officials said airport security had questioned him, and diplomatic security was then sent to resolve the issue.
This latest episode shows that even small difficulties between the two governments are likely to trigger full-blown diplomatic rows, says the BBC's Greg Morsbach in Caracas.