SANTIAGO, Chile — Striking a humble chord, President Obama said Monday that the United States has sometimes taken Latin America “for granted,” but he promised a new relationship that did not consign the region to the status of “junior partner.”

In his speech, Obama laid out a vision for the Latin American-U.S. relationship that was rooted in a shared belief in democracy, stronger cultural ties and expanded trade.

“I believe that in the Americas today, there are no senior partners and there are no junior partners, there are only equal partners. Of course, equal partnerships, in turn, demand a sense of shared responsibility,” said Obama, speaking in the La Moneda Cultural Center, a modern art museum near the presidential palace.

Obama gave the address hours after touching down in Santiago at the midpoint of a five-day Latin America tour that began with a stop in Brazil and ends Wednesday in El Salvador.

The trip — Obama’s first to South America — has unfolded in the shadow of the military conflict in Libya. Still, White House aides said the speech Monday was important in recasting America’s relationship with its southern neighbors.

Fifty years ago John F. Kennedy launched his “Alliance for Progress,” pumping billions of dollars into the Latin American economy. Today, struggling with huge deficits at home, an American president is no longer in position to lavish aid on the region and so must rethink the way north and south cooperate in the new era, aides said.

Obama sought to dispel stereotypes of the United States as an overbearing neighbor dictating terms to South America. He said the American economy is deeply entwined with that of Latin America. Each needs the other to succeed, he said.

“Latin America is only going to become more important to the United States, especially to our economy,” the president said, following a meeting and joint news conference with Chilean President Sebastian Pinera.

“Trade between the United States and Latin America has surged. We buy more of your goods and products than any other country, and we invest more in this region than any other country. … In other words, when Latin America is more prosperous, the United States is more prosperous.”

Obama seemed to acknowledge that the United States faces fierce competition from China for Latin American markets. Brazil’s largest trade partner is China, not the United States.

Obama made the case for his own country, underscoring deep ties within the Western Hemisphere.

“So this is the Latin America that I see today — a region on the move, proud of its progress, and ready to assume a greater role in world affairs. And for all these reasons, I believe that Latin America is more important to the prosperity and security of the United States than ever before,” he said.

But the history between Chile and the United States has had its painful moments. At the joint news conference, a Chilean reporter asked Obama about “open wounds” stemming from the dictatorship of Augusto Pinochet.

Referring to allegations of a U.S. role in Pinochet’s 1973 coup, the reporter said that “many of those wounds have to do with the U.S.” He asked if Obama would pledge U.S. assistance in investigating that part of Chile’s past.

In reply, Obama said that the United States would “like to cooperate” with requests for information about involvement.

“Obviously,” Obama said, “relations between the United States and Latin America have at times been extremely rocky and have at times been difficult. I think it’s important, though, for us, even as we understand our history and gain clarity about our history, that we’re not trapped by our history.”