"We ask legislators from the two parties (Republicans and Democrats), with all due respect, to help us and not mix an electoral political issue with the approval of the treaty," the President said on Friday, Xinhua news agency reported.
"As to the treaty, I believe it has a consensus or greater acceptance among the people of the three nations," he added, referring to Canada, the US and Mexico.
Lopez Obrador said that the Mexico-US-Canada Treaty (T-MEC) must not be held hostage to political differences, as this does not benefit the economic development of the region.
Legislators from the US Republican Party have expressed fears that the possibility of ratifying the T-MEC would be reduced if the process were to continue into next year, due to the 2020 US presidential election and the possibility of an impeachment trial against President Donald Trump.
However, US House Speaker Nancy Pelosi said on Thursday that the US Congress could vote on the treaty this year.
The T-MEC agreement seeks to replace the North American Free Trade Agreement, which took effect in 1994.
To come into effect, the T-MEC needs the approval of the legislatures of all three countries. The Mexican Senate is the only one that has approved it so far.
( With inputs from IANS )