BELFAST, NORTHERN IRELAND — THE threat of renewed violence now looms over Northern Ireland as well as mainland Britain, after a warning by loyalist terrorists that they are ready to match the Irish Republican Army ''blow for blow.''
The so-called Combined Loyalist Military Command, in its first statement since the IRA cease-fire ended a month ago, said Tuesday that IRA attacks cannot continue ''without a telling response.''
The warning by pro-British loyalists, who matched the IRA cease-fire in the fall of 1994 with a truce of their own, comes after days of heightened tension in the province.
''The gunmen are very jumpy,'' says David Irvine, spokesman for the Progressive Unionist Party, which has close links with loyalist paramilitaries. ''Their wives are being followed to schools and such by IRA men, and I think it's all part of the creation of an atmosphere by the IRA in which the unknown is a form of terrorism itself.''
Gary McMichael, leader of the Ulster Democratic Party, which is also close to loyalist outlaws, said the warning showed that ''the dangerous road which the IRA is traveling will inevitably lead to confrontation between the two communities. But it's also saying that now is the time to draw back from the brink.''
Since the end of the IRA cease-fire last month, these two fringe parties have astonished local opinion with their conciliatory tone. Far from calling for violent revenge, they have urged peaceful adherence to negotiation.
''We haven't carried our argument very well,'' concedes Mr. Irvine. ''We're inclined to be viewed as an orange-shirted Fascisti. But that isn't the case. There's substantial diversity within unionism - there's right, left, and center, those who want to move to the future, and those who can't countenance change.''
His latter comment refers to the Rev. Ian Paisley, the charismatic, fire-breathing Protestant politician who for many has come to symbolize the unionists of Northern Ireland.
But the spectrum of unionist belief, held by a clear majority of Northern Ireland's people, is much broader than Mr. Paisley's high profile might suggest. His hard-line Democratic Unionist Party comes second in elections to the biggest and oldest unionist party, the secular Ulster Unionists, who hold nine seats in the British Parliament.
Across the spectrum, unionism is less a philosophy than a statement of British identity. Those who openly profess it are overwhelmingly Protestant. But a sizable minority of the province's Catholics - 1 in 3, in a 1995 study by Queen's University in Belfast - also favor maintaining the union with Britain, albeit quietly.
Out in the Northern Irish countryside, in a largely Catholic village where the green-orange-and-white flag of the Irish Republic flies defiantly, British Parliament member and Ulster Unionist William Ross argues that open discussion has been throttled by 25 years of conflict.
''Given the highly polarized society in Northern Ireland, the chances of the average Roman Catholic standing up in favor of the union are, to put it mildly, remote,'' he says.
Sitting in his heavily fortified farmhouse, on land settled by his family 300 years ago, Ross argues for union with Britain on constitutional grounds.
''If it was right for the American nation to fight a very bloody ferocious civil war in order to maintain the unity of their nation,'' he says, ''Then why should the British state give up its place in Northern Ireland when the majority has decided to stay within the UK?''
The Ulster Unionists say the people of Northern Ireland are well served financially by Britain - public spending is 30 percent higher per head than in the rest of the country - and protected by centuries of democratic tradition.
''After all, the UK is one of the world's great liberal democracies, where you're free to state your opinion,'' Mr. Ross adds.
But down the road, in Londonderry - or Derry, as Irish nationalists call the town - the 300 remaining residents of a Protestant enclave called ''The Fountain'' find it difficult to keep so cool.
Here, where windows are protected by iron grills and the houses girded by a high steel wall to separate them from the Catholic Bogside area, constitutional considerations come second to the fear of fresh violence.
''I dread to think what this place will be if the cease-fire doesn't hold, but we will not be pushed into a united Ireland,'' says Alistair Simpson, a local official in the Apprentice Boys of Derry, a Protestant society formed to commemorate the siege of the town in 1689 by the Catholic forces of King James II.
Here, too, is the widely held fear that the British government will eventually betray the unionists of Northern Ireland by giving in to Catholic nationalists and allow unification with the Irish Republic.
''The majority of the people of the UK want nothing to do with us, because they think that all our fighting and arguing has been trivial.... But what if they had to endure 25 years of what we've had to stand here, our loved ones taken away, bombed out of existence?,'' Mr. Simpson says.
''We can't ignore that, for if we did, we'd be letting down those who have died in the Troubles for this land,'' he adds.