The historic vote followed hours of intense negotations
The Organization of American States has voted to lift Cuba's suspension from the group, paving the way for it to be readmitted after nearly half a century.
Foreign ministers applauded after the resolution was passed following intense wrangling over US demands that Cuba face conditions on rejoining.
"The Cold War has ended," said summit host, Honduran President Manuel Zelaya.
Cuba was suspended from the 34-member OAS in 1962 over its "incompatible" adherence to Marxism-Leninism.
It says it has no interest in rejoining the group - which Fidel Castro has described as a "Trojan horse" for American interference in the region.
But our correspondent in Havana, Michael Voss, says Cuba watched with satisfaction as country after country stood up to the United States in Honduras and demanded that the communist island be allowed to rejoin.
After more than 47 years, OAS foreign ministers and ambassadors - who met in San Pedro Sula, Honduras - came to an agreement that laid to rest what was arguably the most contentious decision in its history, say correspondents.
Cuba was suspended three years after Fidel Castro's revolution
It overwhelmingly declared "without effect" the 31 January 1962 resolution which barred Cuba from the hemispheric body months after Mr Castro had declared it socialist and following the failed Bay of Pigs invasion by the US.
But in a diplomatic compromise which won the backing of the US in the final vote, the resolution called for Cuba's readmission to be based on a "process of dialogue" in line with OAS pro-democracy "practices, proposals and principles".
Despite initial American demands that Cuba should show progress on democracy and human rights before the ban was lifted, US Secretary of State Hillary Clinton welcomed the final outcome as a success.
She said Cuba's re-entry would turn on its "commitment to the organisation's values".
"I am pleased that everyone came to agree that Cuba cannot simply take its seat and that we must put Cuba's participation to a determination down the road - if it ever chooses to seek re-entry," she said.
But some regional heads of state denied the vote imposed conditions as such on Cuba, and hailed the vote as the historic end to an anachronistic measure testifying to Washington's power over the OAS - and, historically, over the region it considered its "backyard".
"What this generation is doing is basically amending history," said Ecuadorean Foreign Minister Fander Falconi, according to Efe news agency.
Since taking office, President Barack Obama has sought to ease tension between the US and Cuba, including ending restrictions on Cuban-Americans visiting and sending money to relatives.
Washington and Havana have also agreed to resume regular talks on migration issues.
But Washington's decision to back the OAS vote incensed some lawmakers, including Representative Ileana Ros-Lehtinen, a Miami Republican on the House Foreign Affairs Committee.
"Rather than upholding democratic principles and fundamental freedoms, OAS member states... could not move quickly enough to appease their tyrannical idols in Cuba," Ms Ros-Lehtinen said.