Trading their warmest words in a half-century, the United States and Cuba built momentum toward renewed ties on Friday, with US President Barack Obama declaring he "seeks a new beginning" - including direct talks - with the island's communist regime. As leaders of the Americas gathered for a summit in the Caribbean nation of Trinidad, the head of the Organization of American States even said he'll ask his group to invite Cuba back after 47 years. In remarks kicking off the weekend gathering of nations - of which Cuba was the only country in the region not represented - Obama repeated the kind of remarks toward the Castro regime that marked his campaign for the presidency. "The United States seeks a new beginning with Cuba," he said at the Summit of the Americas opening ceremony, according to his remarks released in advance by the White House. "I know there is a longer journey that must be traveled in overcoming decades of mistrust, but there are critical steps we can take toward a new day." Analysts cautioned that the week's developments were encouraging but do not necessarily mean normalized relations are around the corner. "This is a thaw, but it's a thaw that's going to take some time," said Michael Shifter of the Inter-American Dialogue in Washington. "I wouldn't look for any dramatic breakthroughs. There's a lot of distrust." Still, President Cristina Fernandez of Argentina, in her remarks to the summit's inaugural session, won applause when she called on the United States to lift the "anachronism that the embargo means today," a reference to the nearly half-century-old US ban on trade with Cuba. "Let's not miss the chance," she said, to build a new relationship with Cuba. The flurry of back-and-forth gestures began earlier this week when Obama dropped restrictions on travel and remittances to Cuba, challenging his Cuban counterpart, Raul Castro, to reciprocate. Obama noted those moves and renewed his promise for his administration to engage with the Cuban government "on a wide range of issues," including human rights, free speech, democratic reform, drugs, immigration and the economy. "Let me be clear: I am not interested in talking for the sake of talking," the president said. "But I do believe that we can move US-Cuban relations in a new direction." In a diplomatic exchange of the kind that normally takes months or years, Castro had responded within hours to Obama's policy changes this week. He extended Cuba's most open offer for talks since the Eisenhower administration, saying he's ready to discuss "human rights, freedom of the press, political prisoners - everything." Cuban officials have historically bristled at discussing human rights or political prisoners, of whom they hold about 200. The United States replied Friday, with Secretary of State Hillary Rodham Clinton offering: "We welcome his comments, the overture they represent, and we are taking a very serious look at how we intend to respond." And OAS Secretary-General Jose Miguel Insulza said he would ask the 34 member nations to invite Cuba back into the fold. Analysts doubted Insulza - known for his political caution - would have done so without a nod from Washington, which contributes a huge portion of the OAS budget. "We're going step by step," Insulza said. He called on the group to annul the 1962 resolution that suspended Cuba because its "Marxist-Leninist" system was incompatible with OAS principles. If two-thirds of foreign ministers agree at a meeting in Honduras next month, the communist government will be reinstated. Obama, in his remarks, rejected what he called a false choice "between sticking to inflexible policies with regard to Cuba or denying the full human rights that are owed to the Cuban people." However, White House spokesman Robert Gibbs made clear that while Castro's new openness to change was welcome, the US wasn't abandoning its demand for Cuba to start making concrete moves toward freedom. "They are certainly free to release political prisoners," he said aboard Air Force One as Obama flew into Trinidad. "They're certainly free to stop skimming money off the top of remittance payments. They're free to institute greater freedom of the press." And Castro didn't retreat from his criticism of US policy, recalling Thursday that the United States has long tried to topple the government that he and his brother Fidel have presided over for 50 years. "That's the sad reality," he said. Said Peter DeShazo of the Center for Strategic and International Studies: "These are very preliminary steps, but they are significant." The US severed all diplomatic ties with Cuba on January 3, 1961, just three months before exiles launched their disastrous invasion of the Bay of Pigs. The last significant effort toward talks were secret negotiations between an aide to then-Secretary of State Henry Kissinger and an emissary from the Cuban Communist Party at a crowded coffee shop at New York's La Guardia Airport on January 11, 1975. Negotiators met in New York hotels and private homes over several months, but the move died when Castro sent troops into Angola.