Talks between Venezuela's President Nicolas Maduro and the opposition are the "last best effort" to finding a peaceful solution to the country's political impasse, a US official says.
US Undersecretary of State for Political Affairs Tom Shannon said if the talks failed, it could lead to both sides "putting people on the streets".
He said such a result would be very dangerous.
It comes after President Maduro rejected calls for an early election.
"From our point of view [the dialogue] really is the last best effort to try to find a negotiated, peaceful solution to this," said Mr Shannon.
He added that it would "unpredictable and can be very dangerous" if Venezuela found itself in a state where either side had to "measure themselves through their ability to put people on to the streets".
Mr Shannon's comments come at the end of a week that saw the progress which had been made at the talks, mediated by a Vatican envoy and former international leaders from Spain, the Dominican Republic and Panama, slowly fall apart.
Mr Maduro remains at loggerheads with the opposition, which dominates the National Assembly after a landslide victory in last year's elections.
He faces calls to step down amid a worsening economic crisis in the country.
Last month, hundreds of thousands of people protested in the capital Caracas after opposition calls for a referendum on Mr Maduro's leadership were rejected.
Mr Maduro was elected in 2013 to replace his late mentor Hugo Chavez, but has seen his popularity plummet to just over 20% amid an unprecedented economic crisis.