Lopez Obrador said Mexico would only take part in the talks in Saudi Arabia, reportedly scheduled to be held over the coming weekend, if both sides were present.
"If there's acceptance from both Ukraine and Russia to look for solutions to achieve peace, we'll participate," the president told reporters at a regular press conference.
Comment: Russia has repeatedly stated it wants peace, it's the US and UK that have deterred Ukraine from engaging in discussions.
"We don't want the Russia-Ukraine war to continue, it's very irrational," Lopez Obrador added, noting that the conflict has caused massive human suffering. "The only thing that benefits from it is the war industry."
Senior officials from up to 30 countries are expected to participate in the talks Aug. 5-6 in Jeddah, the Wall Street Journal reported on Saturday. Russia has not been invited, the outlet reported, citing diplomats involved in the planning.
Comment: This tells us everything we need to know about these peace talks: Russia, that's defending itself against the West and that's engaged in a battle for its future, and which is also winning the conflict, hasn't even been invited.
On Monday, the Kremlin said it would "follow" the meeting but did not currently see conditions for peace talks with Kyiv.
Lopez Obrador has sought to keep Mexico neutral in the war, though his government has backed some major U.N. resolutions criticizing Russia's role in the conflict. Mexico has refused to send arms to Ukraine and has not imposed sanctions on Russia.
In April, Ukraine President Volodymyr Zelenskiy urged Mexican lawmakers to back his plan to end the war, which would include Russia withdrawing its troops from Ukrainian territory.
Lopez Obrador had outlined a separate peace plan last year, which Ukraine opposed, arguing it would have benefited Russia.
Comment: Obrador's position seems to reflect that of some factions within the US, which have resigned themselves to accepting that they've lost the war on Russia, and that it's time to bow out before even greater losses are incurred; and perhaps they'd also like to redirect their dwindling resources to continue provocations elsewhere, such as against China, or pivoting nations in Africa: