The two leaders held a bilateral meeting at the G20 summit and shook hands afterward in front of a swarm of reporters. Both leaders said the meeting was productive, but neither offered specific details about the discussions.
Trump said the United States is in the process of "negotiating NAFTA and some other things with Mexico, but I think we made very good progress."
Peña Nieto agreed, saying the meeting would "continue a flowing dialogue" between the two countries.
Then Trump was asked about his longstanding campaign pledge to build a border wall to curtail undocumented crossings and drug smuggling, and force the Mexican government to pay for it.
He replied with one word, "absolutely," when asked if he still planned to pursue that policy.
Peña Nieto, who has vowed the Mexican government will not pay for a wall, remained silent and the brief media availability ended shortly thereafter.