Mexico's pledge was announced by the White House Tuesday, a day after a similar commitment by Ukraine was unveiled.
Mexico will cooperate with the United States, Canada and the International Atomic Energy Agency to convert highly enriched uranium into lower-grade fuel, BBC News reports.
The two-day summit, the largest hosted by the U.S. government since the end of World War II, has U.S. President Barack Obama meet with 46 world leaders, including Russian President Dmitry Medvedev and Chinese Prime Minister Hu Jintao. It is aimed at ensuring that the world's nuclear materials don't fall into extremists' hands.
"I think at the end of this we're going to see some very specific, concrete actions that each nation is taking that will make the world a little bit safer," Obama said Monday.
The summit in Washington comes a week after the United States and Russia signed a nuclear weapons reduction treaty and only a few days after Obama softened the U.S. nuclear policy, vowing not to use nuclear weapons against countries that don't have them.
The new policy wouldn't spare Iran or North Korea, neither of which was invited to the summit because of the controversy surrounding their nuclear programs. Iran will have its own nuclear security summit this weekend.