Supporters of Mexico's left-wing presidential candidate have pledged to place his rival "under siege" if he is declared winner of the disputed poll.
Police have ringed off Congress following protests
A spokesman for Andres Manuel Lopez Obrador's party said Felipe Calderon would not be able to operate outside his office if he was made president.
Mr Lopez Obrador disputes the official results which give a narrow victory to his rival and wants a full recount.
A partial recount has been completed, but the results are not yet known.
Election officials have until 6 September to declare a president-elect or annul the election.
If declared the victor, Mr Calderon "will be a president under siege... he will not be able to operate outside his office", said Gerardo Fernandez, of the left-wing Democratic Revolution Party (PRD).
Protesters have also pledged to disrupt outgoing President Vicente Fox's last state-of-the-nation address on 1 September. The day "will not be a picnic", Mr Fernandez said.
Mr Lopez Obrador says he has evidence of irregularities during the electoral process.
On Tuesday, his supporters clashed with police outside the Congress building for the first time since they began camping out in Mexico City in protest at the election result.
At least eight people were injured in the scuffles which only lasted a few minutes but saw police use batons and teargas to break up the crowd.
Federal police have denied accusations that they were heavy-handed.
Mr Lopez Obrador has alleged fraud after losing by some 240,000 votes, and has called for a full recount of the 41 million votes cast in the 2 July poll.
Earlier this week, Mr Calderon - the candidate of President Fox's National Action Party - said he was confident the court-imposed recount of votes from 9% of polling centres would confirm his win.
Mr Fox has said he will take all the necessary actions to ensure that whoever is declared president-elect in September is allowed to assume power.