Hundreds of anti-riot police will be on duty today amid fears of street disorder in north Belfast after a big Orange Order demonstration in the city.
Politicians on all sides as well as Northern Ireland Secretary Owen Paterson appealed for calm in the Catholic Ardoyne district where dissident republicans are to protest against a returning parade by some Orangemen from neighbouring Protestant districts.
There has been major trouble before at this particular flashpoint at the end of the traditional Twelfth of July rallies when police were attacked with petrol bombs and bricks by gangs of masked men opposed to the Sinn Fein peace process strategy of Gerry Adams and Martin McGuinness.
The Chairman of the Police Federation, Terry Spence, who represents almost 7,000 rank and file officers who called for restraint, said: "No yard of road is worth either an injury or the death of a police officer or a member of the public. The parade should not become a day of shame for both communities."
The Parades Commission which adjudicates on contentious marches has ruled the Orangemen must return along the Crumlin Road past Ardoyne by 4pm.
Police say that deadline will be rigorously enforced, but the Orangemen insist it is an impossible one to meet and with republicans due to stage a rally an hour and a half later, community representatives are fearful of trouble.
On Wednesday night Orange Order leaders in the city said they had come up with a solution to ensure the return parade would pass off peacefully, but they said details of the plan would not be revealed until later at a rally on the southern outskirts of the city.
Mr Paterson has warned the price Northern Ireland will have to pay if trouble escalates into a full-scale riot and what it might mean for those involved and detained by police.
He said: "The consequences of breaking the law would not only be bad for Northern Ireland, its global reputation and attractiveness as a place to visit and do business. It would also be immensely damaging for anybody who engages in a few moments of madness, as the recent very stiff sentences handed down to people who participated in violence last year demonstrate.
"We all have a responsibility, working together, to ensure a successful and enjoyable Twelfth and to keep Northern Ireland moving forward. This requires real leadership in Northern Ireland at all levels and right across the community."