The bill was due to be approved by Dec. 15, but it has been delayed to next year, with the Supreme Court setting a new deadline of April 30 for the law to be passed, according to local media.

Lopez Obrador said legislators requested a delay as time had run out before the current session in Congress ended this month, meaning there was not enough time to review the bill.

"The period was practically over but they are matters of form and not substance," Lopez Obrador said in his morning daily press conference, adding that the issues will be "resolved" in the next session due to start in February.

The bill, which would mark a major shift in a country bedeviled for years by violence between feuding drug cartels, easily passed the Senate in a vote last month, and would create a huge new legal market for marijuana.

Lopez Obrador's left-of-center Morena party, which backed the initiative, holds a majority in both chambers of Congress with its allies.

"It is nothing more than a matter of mistakes that were made, lack of precision on quantities and there can be no contradictions in the law itself," Lopez Obrador said, referring to how much cannabis citizens can possess legally.

The legislation responds to a Supreme Court order mandating that use of the drug be regulated, although the process has been subject to repeated delays, frustrating legalization advocates. Nevertheless, the legislation is ultimately expected to pass.