PORT OF SPAIN, Trinidad and Tobago (CNN) - President Barack Obama concluded the 34-nation "Summit of the Americas" Sunday by calling it a "very productive" meeting that had proven hemispheric progress is possible if different countries are willing to set aside "stale debates and old ideologies."
He cited a potential thaw in relations between the United States and longtime adversaries Cuba and Venezuela, but said the ultimate test "is not simply words, but deeds."
Leaders did not "see eye to eye" on some important issues, but the meeting proved it is possible to "disagree respectfully," the president said.
Speaking to reporters before returning to Washington, Obama highlighted the importance of using American diplomacy and development aid in "more intelligent ways."
He had reached out to the Cuban government before the summit by lifting all restrictions on the ability of individuals to visit relatives in Cuba, as well as to send them remittances.
Obama noted that the leaders of other countries at the summit highlighted Cuba's program sending "thousands of doctors" throughout the hemisphere. A number of countries depend heavily on Cuba's medical assistance program.
"It's a reminder... that if our only interaction with many of these countries is drug interdiction - if our only interaction is military - then we may not be developing the connections that can over time increase our influence and have a beneficial effect," he said.
Obama called Cuban President Raul Castro's recent indication of a willingness to discuss human rights issues "a sign of progress." But he said the Cuban government could send a much clearer, more positive signal by releasing political prisoners or reducing fees charged on remittances Americans send to relatives in the country..
Change in Cuba will not come quickly, Obama added, but it is good for other countries to see that "we are not dug in into policies that were formulated before I was born."
Turning to Venezuela, Obama conceded vast differences with Hugo Chavez on economic and foreign policy issues. But he said the strategic interests of the United States would not be endangered by having a "more constructive relationship" with the oil-rich nation.
Asked what an "Obama Doctrine" would be, he declined a specific answer, but outlined broad principles such as the importance of listening to other countries. The United States, Obama said, remains the most powerful nation in the world, but cannot solve problems such as climate change, drugs, and terrorism on its own.
"If you start with that approach, you are inclined to listen, and not just talk," he said.
Obama added that the United States is at its best when it stands "for universal ideals (such as) freedom of speech and religion. If we confess to having strayed from (our) values, it strengthens our hand (and) allows us to speak with greater moral force and clarity."
The president was criticized over the weekend by several leading Republicans - as well as former CIA director Michael Hayden - for releasing four Bush-era memos outlining terror interrogation methods used against suspected al Qaeda operatives.
Obama said when he released the documents Thursday that the U.S. needs to "right its course in concert with our core values."