Mischa Gaillard, the opposition coalition spokesman, said: "We don't want confrontation. The police have not done their duty to serve and protect. Since our strategy is a peaceful one, we have cancelled the demonstration."
The government of President Aristide has been rocked in the last week by a series of armed insurrections which have seen rebels take over around a dozen towns.
The president's supporters, armed with baseball bats and wearing balaclavas, claimed they were protecting democracy. "They don't want elections. They want to take over. We are here to protect the police because they are in a minority" said Amos Giffrard, 50.
"Democracy hangs in the balance," he added.
"The opposition came to take over the police station. We came to stop these terrorists," said Bernabe Mervil, 33.
The political situation remained volatile across the country yesterday with the government and the opposition preaching peace but increasingly dependent on violent gangs to strengthen their bargaining position.
The government has regained control of three towns, but with no army and only 4,000 police Mr Aristide's grip on power remains precarious.
The death toll rose to 45 after three anti-government rebels were executed by Aristide supporters in St Marc, a town the government recaptured on Monday.
Meanwhile in the country's second city, Cap Haitien, Aristide supporters also erected blazing barricades to block a feared rebel incursion.
Mr Aristide has branded attempts to move him as a coup d'état. "I will leave the palace on February 7 2006," he said in his first news conference since the uprising began.
The opposition in Port-au-Prince, a coalition of human rights campaigners, students and business people, is demanding Mr Aristide's immediate resignation and a two-year transitional government to replace him. They have distanced themselves from the armed uprisings elsewhere in the country, a claim the government has dismissed.