Maduro used the political shorthand of "colonialism" to rail against perceived U.S. influence in Central and South America and the Caribbean during a meeting of the Community, known by its Spanish acronym CELAC -- Comunidad de Estados Latinoamericanos y Caribenos.
"I'm very motivated since this is going to be a historic summit, which will help to consolidate CELAC," Maduro said. "Venezuela has come to Havana with its proposals and contributions, which is to declare the region 'free of colonies' and invite Puerto Rico to formally join the family."
There was no immediate response to Maduro's comment from the Commonwealth of Puerto Rico, often described as an "unincorporated" U.S. territory. Cuba is passing the rotating presidency of CELAC to Costa Rica as part of an effort to woo Costa Rica to become more proactive in the group.
Cuban host President Raul Castro called on regional leaders to work for integration but without Canada or the United States. CELAC members include all regional states except Canada and the United States.
Castro called for an independent Puerto Rico and the end of the 52-year-old U.S. economic embargo on Cuba, the longest in history.
The meeting was marked by muted protests and criticism of Cuba's human rights record by international advocacy groups including Amnesty International, which called on Cuba to end its "campaign of repression against opponents and dissidents" and demanded demonstrations be allowed in the capital during the conference.
At least 40 people were detained before or during protests at a central Havana park, dissident blogs and media reported.
The tone for the left-wing and populist pronouncements in Havana was set by an unrelated event -- CELAC member Nicaragua's decision to dispense with the term of presidential office, making way for President Daniel Ortega to secure a third term.
Castro said regional states seeking to free themselves of outside influence should follow Cuba's example and build literacy and healthcare. Opposition critics say those achievements don't cancel out the lack of basic freedoms and rights in the Caribbean state and in other CELAC member states, including Venezuela.
As "the legitimate representative of the interests of Latin America and the Caribbean" CELAC should set "a new regional and international co-operation paradigm," Castro said.
In two distinct signs of regional change, U.N. Secretary-General Ban Ki Moon made a low-key speech without mentioning the rights issues and Jose Miguel Insulza, secretary-general of the Washington-based Organization of American States, attended as an observer, in what was reported to be the first visit by an OAS secretary-general to communist Cuba.
A joint declaration by the participating member states is expected to reiterate comments raised by Castro and Maduro.