Calls for legalization -- expected at the Summit of the Americas, which began Saturday -- come in a region where the U.S. demand for illegal drugs has led to rampant violence as well as political and economic turmoil, The Los Angeles Times reported.
Colombian President Juan Manuel Santos wants the 33 leaders at the summit to consider legalizing and regulating marijuana and possibly cocaine, as alcohol and tobacco are, the Times said.
Guatemalan President Otto Perez Molina said after a pre-summit meeting with leaders from Costa Rica and Panama that he had called for a "realistic and responsible" discussion of drug decriminalization.
"We cannot eradicate global drug markets, but we can certainly regulate them as we have done with alcohol and tobacco markets," he wrote in the British newspaper the Observer on April 7.
"You haven't had this pressure from the region before," said Michael Shifter, president of the Inter-American Dialogue, a think tank in Washington. "I think the [Obama] administration is willing to entertain the discussion, but hoping it doesn't turn into a critique of the U.S. and put the U.S. on the defensive."
White House officials have said Obama won't change his drug policy. The Times said administration officials hope discussion of legalization remains private.
On Saturday, Obama was expected to tell fellow leaders the United States is the largest foreign investor in Latin America and that he planned "deeper economic partnerships" in the region, Voice of America reported.
Obama arrived in Cartegena, Colombia, Friday night in advance of the summit.