Mexico was the only member of the 14-country Lima Group -- which includes several top Latin American powers and Canada -- not to sign a statement Friday calling on Maduro to transfer power to Venezuela's democratically elected, opposition-controlled legislature, instead of starting a new term this week.
That marked a major diplomatic shift for Mexico, the world's largest Spanish-speaking country. Until Lopez Obrador, an anti-establishment leftist, took office in December, Mexico had been one of the most outspoken critics of Maduro's socialist government.
Lopez Obrador fended off criticism over the move, saying his administration was simply following a policy of "non-intervention."
"We're in favor of dialogue, without a doubt," he told a press conference.
"However, what we can't do is condemn a foreign government, because that violates the principle of non-intervention.... It's not about (ideological) sympathies. It's about our foreign policy and our foreign-policy principles."
He added: "We are going to be respectful of all the world's governments and peoples."
Maduro has presided over a spiraling political and economic crisis in Venezuela since taking over from his mentor, the late leftist firebrand Hugo Chavez, in 2013. He won a new six-year term in May in an election marred by irregularities.
The Lima Group says it will not recognize a new Maduro-led government. Maduro's administration accused the regional bloc on Friday of trying to foment a coup at the behest of the United States.
The group's meeting in the Peruvian capital last week was the first for Lopez Obrador's government.
The Lima Group's other members are Argentina, Brazil, Canada, Chile, Colombia, Costa Rica, Guatemala, Guyana, Honduras, Panama, Paraguay, Peru and Saint Lucia.