A mass rally by mainstream Muslims demonstrating against controversial cartoons depicting the Prophet Muhammad as a terrorist is to be staged.
Organisers and police are expecting at least 10,000 people to gather in central London's Trafalgar Square.
Public figures from across the political spectrum are due to speak.
The event aims to explain the views of moderate Muslims towards cartoons published in a Danish newspaper which led to worldwide protests.
Organisers also said it aims to dissociate the mainstream Muslim community from a "minority of extremists".
The rally on Saturday afternoon, called United Against Incitement and Islamophobia, has been organised by the Muslim Council of Britain and the Muslim Association of Britain.
It has the backing of a number of Christian organisations and the backing of the Mayor of London.
Mayor Ken Livingstone singled out football thugs and extremists and warned them to stay away, saying police would halt any attempt to disrupt the demonstration.
Organiser Anas Altikriti, of the Muslim Association of Britain, said he was confident the demonstration would not be taken over by extremists.
He told BBC Five Live: "Our stewards are very vigilant, we're working very closely with the police plus we have made absolutely sure that there will only be one official slogan on our T-shirts and on our placards, and that is 'united against incitement and united against Islamophobia' - anything else is not down to the organisers."
'Civilised manner'
Sundus Malik, who will travel from Manchester to take part in the rally, stressed the event would be peaceful.
"We are peaceful people and we're there to tell the world in a peaceful manner that something has got to be done about this," said Ms Malik.
She added: "We would like to send our message across calmly and in a respectful manner - unlike the cartoons which were obviously Islamophobic and which did not exercise responsibility or judgement at all."
Scotland Yard said it has been working with organisers all week to plan the operation, expected to involve 500 officers.
Ch Supt David Commins told BBC News: "The initial approach is if people see placards which they think offend them, we will expect the organisers and the stewards to deal with that.
"Clearly policing a rally where there are 10,000 people, making a decision about whether to arrest or not to arrest is a very complex one."
Protests held in London last week sparked outrage when demonstrators carried placards with strong messages - the Metropolitan Police said some protesters could be charged with "incitement to murder".
Doctor Azam Tamimi, who is the director of the Institute of Islamic Political Thought, is due to speak at the demonstration and said it would be peaceful.
"The main purpose of the rally today is to object to what has been going on in a civilised manner.
"We have the right to be angry, but we have to do it within the remits of the law, and we have to respect the rights of others," he said.