Venezuelan Foreign Minister Nicolas Maduro has accused US officials of detaining him and threatening him at an airport after he visited the UN.
Mr Maduro says he was told to remove his clothes
Venezuela made a formal complaint to the US authorities and to the UN secretary general.
The US apologised for the "incident", without saying what happened.
A US Homeland Security Department spokesman told AFP news agency there was no evidence Mr Maduro had been arrested or taken into custody.
Mr Maduro told Venezuelan television that he was detained for an hour-and-a-half and his passport and plane ticket were temporarily taken away.
He said he was verbally abused, threatened with being strip-searched, and that authorities at one point ordered him and other officials to spread their arms and legs and be frisked.
There appears to have been a row between security officials and Mr Maduro as he was passing his belongings through an airport metal detector, the BBC's Greg Morsbach reports from Caracas.
"There's no evidence to support the claim that his travel documents were taken away, there's no evidence to support the claim that he was assaulted, there's no evidence to support the claim that he was somehow arrested or taken into custody," US Homeland Security Department spokesman Russ Knocke told AFP.
But the US State Department later issued an apology:
"The State Department regrets this incident. The United States government apologised to Foreign Minister Maduro and the Venezuelan government," department spokesman Gonzalo Gallegos said.
An official said the Venezuelan minister was asked to go through a second, routine screening and after that he could have caught his flight home but decided to stay in New York.
This latest episode shows that even small difficulties between the two governments are likely to trigger full-blown diplomatic rows, our correspondent adds.
President Hugo Chavez said Mr Maduro had been questioned about his alleged role in a failed Venezuelan coup attempt in 1992, led by Mr Chavez.
Mr Chavez said suggestions that his minister had been involved in the 1992 coup were "absolutely false".
Mr Maduro phoned Venezuelan television station Globovision on Saturday to tell them he had been detained.
Mr Mauro said the situation had deteriorated when he informed officials that he was Venezuela' s chief diplomat.
He said he was confined to a small room and told to remove his clothes.
"They started insulting, yelling and brought a police officer... and they started threatening us," Mr Maduro added.
The country's Vice-President, Jose Vicente Rangel, said there was no doubt that the detention was connected to Mr Chavez's speech at the General Assembly on Wednesday in which he mocked US President George W Bush as "the devil."
It was an "unspeakable" attack, he said.