Rival lawmakers in Mexico City have camped out for a third day in the congress building ahead of plans to inaugurate Felipe Calderon as president.
Opponents of Mr. Calderon accuse him of fraud in the July vote, and have vowed to block his inauguration Friday. Mr. Calderon's supporters in congress say they will ensure the ceremony occurs as scheduled.
Officials say recent negotiations failed to reach an agreement to end the standoff.
Meanwhile, Mexico's military has deployed soldiers to the capital to guard against violence during the ceremony.
Leftist politician Andres Manuel Lopez Obrador has rejected tallies that show him narrowly losing to Mr. Calderon in the presidential vote. He is calling on supporters to rally in the capital and disrupt the planned inauguration.
Some information for this report was provided by AP.