U.S. Vice President Mike Pence told the Summit of the Americas in the Peruvian capital that immediate action was needed as Venezuela gears up for presidential elections on May 20 that have been condemned by many regional leaders as a farce to legitimize Maduro's rule.
For the first time, the United States backed a statement by heads of state from the Lima Group of nations - established last year to seek a peaceful end to Venezuela's political turmoil - which called on Maduro to release political prisoners and hold free elections.
Despite an economic collapse that has driven an estimated 3 million people to flee his once-prosperous OPEC nation, Maduro is expected to win next month's poll.
Venezuela's two most popular opposition leaders are banned from competing and electoral authorities are stacked with government supporters.
"The United States of America will not stand idly by as Venezuela crumbles," Pence said in a speech. "Every free nation gathered here must take stronger action to isolate the Maduro regime. We must all stand with our brothers and sisters suffering in Venezuela."
The statement by the Lima Group voiced alarm at an exodus of migrants from Venezuela and urged governments to intensify actions aimed at restoring democracy.
Washington has already targeted senior members of Maduro's administration with sanctions due to accusations of corruption and rights abuses.