Police and British soldiers threw a ring of steel around this grim Northern Ireland town Friday, posting armored cars and checkpoints on every road in advance of this weekend's showdown with Protestant marchers.

British Prime Minister Tony Blair scrambled to safeguard the peace accord he helped broker, waging telephone diplomacy with officials and church leaders. He sought a compromise between Protestant Orangemen - who are determined to hold their annual parade from Drumcree church down rural Garvaghy Road on Sunday - and the road's Catholic residents. Catholics along the route are demanding that British security forces stop the march.But Blair's appeals for somebody to back down for the sake of peace fell on deaf ears in Port-a-down, the most explosive battleground on the Northern Ireland map.

This province's delicate embrace of a peace process designed to bring British Protestant and Irish Catholic politicians together clashes with the mutual contempt and fear that color everyday life in this segregated town.

Portadown and surrounding North Armagh form the heartland of the Orange Order, the Protestant fraternal group founded 203 years ago to defend the "reformed faith" against "the false doctrines of Popery," as its oath declares.

Orangemen were instrumental in founding Northern Ireland 77 years ago, but today they see their organization and the state struggling to survive.

"This seems to be the year they have decided to break the Orangemen. But if they think that, they are very mistaken," said Denis Watson, Armagh's senior Orangeman, confirming that his followers will defy a government-appointed Parades Commission's order to stay away from Garvaghy Road after their church service Sunday.

The confrontation is more entrenched today than when Catholics first tried to block the march in July 1995. In the past two years, the protests have triggered widespread violence across Northern Ireland.