The U.S., the world's second-largest emitter, reiterated its intention to ratify this year, as did Canadian Prime Minister Justin Trudeau and the leaders of Mexico and Australia.
The No Circulation Program ordered in Mexico City is effective in reducing pollution peaks, but is insufficient to address the long-term environmental problems of the metropolis.
Continued exposure to air pollutants may increase about 10% the chance of developing lung cancer.
Factories across greater Mexico City were ordered to cut emissions by 30 to 40 percent, and gas stations without vapor recovery systems were told to close.
Many vehicles will be unable to travel in Mexico City on Tuesday.
The situation affects 15 municipalities in the State of Mexico and eight metropolitan districts.
Until now vehicles have been exempt from Mexico City's "no circulation" rules if owners obtain a holographic sticker from a smog-check center certifying them as lower-emission.
The authorities declared the city's first Phase 1 pollution alert since 2005 on Monday.
Exposure to air pollution for just a month or two may still be enough to increase the risk of developing diabetes, especially for obese people.
Environment Secretary Alejandro Pacchiano said if conditions don't improve, further measures may be considered such as suspending industrial activity at factories.