Mexico President Andrés Manuel López Obrador declined to congratulate Biden, saying that the election needs to be “legally resolved.”

With regard to the US election, we are going to wait until all the legal matters have been resolved,” López Obrador, commonly known as Amlo, said at a news conference.
“I can’t congratulate one candidate or the other. I want to wait until the electoral process is over.”

Let me add here that Mexico is the United States’ top trade partner, with over $600bn of annual two-way commerce, and the bilateral relationship Mexico enjoys with the U.S is by far the most important for Mexico.