Mexico's leftist presidential candidate Andres Manuel Lopez Obrador says he rejects the decision to declare Felipe Calderon the winner of the country's presidential election.
Lopez Obrador was speaking to supporters camping in Mexico City's historic Zocalo square.
Mexico's Federal Electoral Tribunal said unanimously Tuesday that Mr. Calderon won the most votes in the July 2 polls. Under Mexican law, the ruling cannot be appealed. Mr. Calderon won by slightly more one half of one percent of the vote.
Lopez Obrador and his supporters had claimed massive voter fraud and challenged earlier preliminary results. He has said he intends to establish a parallel government. His supporters are planning a rally on September 16th, Mexico's independence day.
The election and claims of fraud represent a serious challenge to the country's fledgling democracy, just six years after President Vicente Fox's dramatic victory ended decades of one-party rule.
The White House issued congratulations to Mr. Calderon on Tuesday after his victory was announced.
Some information for this report was provided by AFP, AP and Reuters.