CARTAGENA, Colombia -- Barack Obama will be on the defensive heading into this weekend's Summit of the Americas, with the United States clinging to positions opposed by most Latin American and Caribbean leaders as its influence in the region wanes.

The president can expect even some allies to protest U.S. insistence on excluding communist Cuba from the gathering. There will be vigorous discussion on drug legalization, which the Obama administration opposes.

And Obama can expect to be in the minority in his opposition to Argentina's claim to the British-controlled Falkland Islands.

Obama remains popular in Latin America, but many of his positions are not.

On top of that, key issues Latin American leaders are seeking answers for, such as Cuba, drug trafficking and immigration, may prove to be contentious during a U.S. election year.

He will have to convince them the United States remains relevant to their countries.

"I think that the United States has to turn around and really look at Latin America with greater responsibility," Guatemalan President Otto Perez Molina said in Cartagena Friday. "In reality, I feel that the agenda of the United States and the agenda of Latin America countries, instead of moving in parallel to each other, or converging, are taking paths that separate them, that distance them."

In large part, declining U.S. influence comes down to withering economic clout, as China gains on the United States as a key trading partner throughout the region. In fact, Latin America weathered the recent economic crisis by exporting soybeans, iron ore and other commodities to China.

"Most countries of the region view the United States as less and less relevant to their needs -- and with declining capacity to propose and carry out strategies to deal with the issues that most concern them," the Washington-based think tank the Inter-American Dialogue noted in a pre-summit report.

Colombian President Juan Manuel Santos, the summit host, said he's advised his U.S. counterparts to pay heed to the changes in Latin America.

"What I've said . . . is 'You'd better look to the south,' because their long-term strategic interests are in Latin America, not in distant lands," Santos said.

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