They will also seize the finances of website operators who peddle child pornography and freeze the credit cards of their customers.
"We want to create the equivalent of a beat cop for the Internet," said the UK's National Crime Squad Assistant Chief Constable Jim Gamble.
Police from Britain, the United States, Canada and Australia are to form a global taskforce with the primary aim of stopping paedophiles luring children into offline encounters.
"This should not be viewed as a Big Brother tactic - this is about police becoming more visible on the Internet," Gamble said on Wednesday.
Under the plan, an officer would appear in a chat area from time to time to observe conversations and would be identified with a type of "cyber badge" or icon for the "Virtual Global Task Force" to let everyone in the chatroom know.
"We want to give the potential predator the idea that we are present to make them think 'will I loiter here or will I flee from that particular chatroom?'"
The problem of paedophile "grooming" of children in chatrooms has been growing.
"We want to create the equivalent of a beat cop for the Internet... We want to give the potential predator the idea that we are present to make them think 'will I loiter here or will I flee from that particular chatroom?'"
UK National Crime Squad
Last year, Microsoft's MSN Web portal shut down chatrooms in nearly every country where it operated, saying they had become a haven for paedophiles and spam-peddlers.
The move was greeted with mixed emotions. Child safety groups welcomed it, but others feared that the criminal element would burrow further underground to prey on victims.
Gamble also said the taskforce would begin working with banks, credit card associations and internet service providers to identify websites that sell access to illegal content, notably child pornography.
The aim is to freeze the assets of these website operators.
"We are looking to strip the money out of organised crime," he said.
Gamble had no timeframe for when he would like to see the initiative begin.
The National Crime Squad is working, among others, with America's Federal Bureau of Investigation, The Royal Canadian Mounted Police and the Australian Federal Police.