The second and final day of the Summit of the Americas takes place in Cartagena, Colombia, on Sunday, where leaders from more than 30 North and South American countries are discussing several topics, such as bolstering economic ties and who should be part of future discussions.

Yet the war on drugs that has drawn some of the sharpest distinctions among leaders at the two-day gathering.

On Saturday, leaders debated how to address drug trafficking and violence in the hemisphere, with several calling for new approaches -- something U.S. President Barack Obama said he was open to, though he closed the door on legalization.

Colombian President Juan Manuel Santos compared continuing the existing policies to address this issue to being on "a stationary bike" -- making little progress, despite ample effort.

"I think the time has come to simply analyze if what we are doing is the best we could be doing, or if we can find an alternative that would be more effective and less costly to society," he said. "This is a topic of extreme political sensitivity."

Santos added, "One extreme can be to put all users in prison. On the other extreme, legalization. In the middle there may be more practical policies, such as decriminalizing consumption but putting all the efforts into interdiction."

The possibility of drug legalization has gained traction in Central America, which is being squeezed between suppliers to the south and consumers to the north.

Yet the idea goes against decades of the prohibitionist policy backed by the United States, which is largely followed and enforced in Latin America and the Caribbean.

Obama voiced his view that legalizing drugs isn't a valid option in the United States twice on Saturday -- first during a meeting of business leaders alongside Brazilian President Dilma Rousseff and Colombian President Juan Manuel Santos and later during the hemispheric event's opening day session.

"I think it is entirely legitimate to have a conversation about whether the laws in place are doing more harm than good in certain places," he said at the meeting of business leaders. "I personally, and my administration's position is, that legalization is not the answer."

He reiterated that position while talking at the summit itself, saying "the United States will not be going in this direction."

Nations in the Americas -- including the United States -- have "mutual responsibilities" to tackle the issue, Obama said. To that end, he announced an increase to more than $130 million of funds dedicating to bolstering security and going after narco-traffickers and "gangs" in the region.

In addition to the drug issue, a major talking point in the run-up to the summit was on leaders from the hemisphere who are not present in the coastal city of Cartagena, Colombia.

Venezuela's foreign minister told reporters Saturday that Venezuelan President Hugo Chavez will not attend because of health reasons. Chavez had recently returned to his country from Cuba, where he underwent cancer treatment.

Cuba, which is not a member of the Organization of American States, was not invited to join the leaders. But there was a last-minute push by Ecuador's leftist President Rafael Correa to get Cuban leader Raul Castro a seat at the table.

Correa boycotted the summit because of Cuba's exclusion.

Santos, a key U.S. ally, said in his opening remarks Saturday that it was time to overcome such issues -- calling it unthinkable if Cuba is not part of the next Summit of the Americas, as well as nearby Haiti.

At the business leaders' meeting, Rousseff spoke of a need for a "virtuous relationship" based on respect and equality among economies, while Santos said he welcomed a "change of mentality in relations between north and south."

Obama pointed out one change he'd like to see: "I think in Latin America, part of the change in mentality, is also not always looking at the United States as the reason for everything ... that goes wrong."

There are many examples of increased cooperation between the United States and Latin America, but they are not always flashy and don't draw the same type of attention that conflicts do, Obama said.