US President Donald Trump on Monday warned Caracas of "economic actions" if Nicolas Maduro delivers on his bid to rewrite the constitution, calling the Venezuelan president a "bad leader who dreams of being a dictator."

"The United States will not stand by as Venezuela crumbles," Trump said in a statement. 

"If the Maduro regime imposes its Constituent Assembly on July 30, the United States will take strong and swift economic actions," he said, without elaborating on what those actions would be.

Trump praised the Venezuelan opposition's unsanctioned Sunday vote that saw millions of voters reject Maduro's plan, saying "their strong and courageous actions continue to be ignored by a bad leader who dreams of becoming a dictator."