Venezuelan President Nicolas Maduro skipped a visit to the United Nations citing “threats” against him.
He had been scheduled to speak at the UN General Assembly on Wednesday, but was removed from the list of speakers.
Speaking from the Venezuelan capital, he said there had been “serious provocations that could threaten his life”, but gave no details.
Mr Maduro is a strong critic of the US and has previously accused Washington of plotting against him.
The president announced his intention to cancel his appearance at the United Nations during a stopover in Vancouver, on his way back from a visit to China.
“When I got into Vancouver I evaluated the intelligence which we received from several sources.
“I decided then and there to continue back to Caracas and drop the New York trip to protect a key goal: safeguarding my physical integrity, protecting my life,” he said.
Mr Maduro accused two former US officials of being behind the “provocations”.
“The US government knows exactly that these people were behind a dangerous activity being plotted in New York.
“The clan, the mafia of Roger Noriega and Otto Reich once more [conspired against me],” he said in a statement broadcast on Venezuelan national television and radio.
Mr Reich was the US Assistant Secretary of State for Western Hemisphere Affairs under President George W Bush. Mr Noriega succeeded Mr Reich in the post.
Both have in the past been the target of allegations made by Mr Maduro. Mr Noriega called the accusations “ridiculous and unfounded”.
Mr Maduro said he would not reveal details of the plot in order not to compromise his information source.
The US State Department dismissed Mr Maduro’s allegations.