"It is a fundamental debate," he said.
"You have to analyse carefully the pros and cons and key arguments on both sides."
However, Mr Calderon, who has waged a war on drugs since taking office in 2006, said he personally opposes the idea of legalisation.
His new attitude comes as official figures released this week put the number of drug war related murders at 28,000 in the past four years.
The figure represents an increase of about 3,000 on the previous estimates.
Most of the dead are thought to be victims of clashes between rival gangs.
The figures show that there have been 963 clashes between the security forces and drugs gangs since Mr Calderon took office, an average of almost one a day.
In the face of the growing death toll, Mr Calderon said that some people were urging him to leave the cartels alone.
"Really, they are telling me, 'Mr president, don't bother the criminals'," he said.
Mr Calderon called that "simply an unacceptable option."
Last year, three former presidents, Ernesto Zedillo of Mexico, Cesar Gaviria of Colombia, and Fernando Henrique Cardoso of Brazil, said the US-led war on drugs had failed and called for the legalisation of marijuana to be considered.
- Article from The Telegraph.
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