Police and British soldiers transformed the town of Portadown into a military camp Saturday, wrapping its Catholic enclave in an armored cocoon and stringing barbed-wire barriers across pastures to thwart Protestant marchers.

Politicians from all sides said they hoped Sunday's annual showdown over who "owns" Portadown's Garvaghy Road - the Catholics who live alongside it, or the Orangemen who view this Protestant town as their spiritual home - would not spark riots across Northern Ireland as it has the past two years."We do not want to see violence on our streets. We do not want the two sides of our community to embark on a collision course where all will be losers," said David Trimble, an Orangeman and leader of the north's major pro-British party, the Ulster Unionists, which has formal links with the 80,000-strong Orange Order brotherhood.

Trimble spoke alongside Seamus Mallon, deputy leader of the main moderate Catholic party. Together they head Northern Ireland's new power-sharing Assembly, the main pillar of April's multiparty agreement on how Northern Ireland should be governed.

Mallon urged both the protesters and the Portadown Orangemen to demonstrate "tolerance, restraint and generosity."

At his English country retreat, Prime Minister Tony Blair blamed the deadlock on the refusal of the Orangemen to talk directly with the Catholic protesters and on the "very entrenched positions" of both sides.

Alistair Graham, chairman of the Parades Commission that ordered Orangemen to avoid Garvaghy Road, blamed the failure to defuse the showdown on "the strong personalities that exist on either side" - an apparent reference to Portadown's Orange district master, Harold Gracey, and the Catholic protest leader, former IRA prisoner Breandan MacCionnaith.

Orangemen insist they must be allowed to parade along Garvaghy Road into town from their rural Drumcree Anglican church. Since 1807, as part of their annual demonstration of Protestant solidarity, they have marched that route beneath emblems of a British crown on an open Bible.

Portadown and surrounding North Armagh form the heartland of the Orange Order, a Protestant fraternal group founded in 1795 to defend the "reformed faith" against "the false doctrines of Popery," according to its oath.

Ronnie Flanagan, commander of Northern Ireland's predominantly Protestant police force, said Saturday that no level of civil disobedience by Orangemen would achieve their goal.

"There are plenty of legitimate avenues through which such people can protest, legitimately and peacefully, against this decision," he said.

MacCionnaith has organized his Catholic protesters to form a round-the-clock picket alongside Garvaghy Road.