Is David Trimble on the verge of losing control of his party? The mood in last Thursday's Assembly party meeting was decidedly uncertain. Many were left with the impression Mr Trimble wanted to do a deal with the Prime Minister on cross-Border bodies but his party wouldn't let him.

This impression has persisted, even though the unionists have counter-attacked and challenged Seamus Mallon's version of the negotiations.

But the gap between the two sides is narrow. The SDLP's demands in the area of investment (always a bargaining counter) have been shelved. This is unsurprising. Even at the time of the Framework Document there was no British government support for such a proposal, partly because of knock-on effects in sensitive areas such as taxation. There is no evidence Tony Blair has any different view on this topic from John Major; indeed, there is considerable evidence suggesting their views are identical. But the SDLP has successfully increased the agenda of cross-Borderism; we now have an area of significant economic activity - trade - included, as opposed to the rather watery minimalism of aqua-culture and food safety.

The UUP leadership appears relatively relaxed about this. There is confidence such a deal would work out satisfactorily.

After all, David Trimble has effectively been allowed to negotiate the final elements of the North-South package in the absence of a shadow executive including Sinn Fein. Only a few weeks ago, conventional wisdom had it this would not or could not happen.

In fact, both governments are keen to have the cross-Border deal done before the Christmas holidays. Burned into the British government's memory, in particular, is the bad memory of Christmas past: in 1995 the cycle of "Direct Action Against Drugs" murders warned the first IRA cessation was ending.

In 1997, the Billy Wright murder unleashed violence which almost destroyed the talks process. There are ominous rumblings again this year: the tabloids talk of the possibility of a rebirth of direct action against drugs-type activity. Unionists are receiving a definite signal from Tony Blair that the fine point of cross-Borderism (as opposed to decommissioning where there is a strong moral case) is the worst possible issue to stick on. The unionist leadership obviously agrees.

All the key parties - Ulster Unionist, SDLP, British and Irish governments - have an interest in being able to say to the republican movement: "Here is the offer - two ministries plus cross-Border bodies - now please move on decommissioning."

After all, as long ago as October 1994, according to Sean Duignan's One Spin on the Merry Go-Round, Martin McGuinness told Albert Reynolds: "We know the guns will have to be banjaxed".

Mr Trimble often cites this text with approval - though he is well aware of the reality that republicans have not made the range of political gain expected from the peace process; hence, the current refusal to "banjax" the guns.

For matters to progress, the Unionist Assembly party has to be convinced. Last week, some claimed they did not have sufficient information to make a decision. Others were embittered by a series of antagonistic run-ins with the SDLP. The question is posed: "Was the party leader doing enough to allay reasonable concerns?"

The history of unionist leadership throws up several worrying examples. Col Saunderson, Capt Terence O'Neill and Mr Brian Faulkner all gave more attention to the high political arena - essentially good relations with Westminster - than they did to the demands of local political sentiment.

Saunderson, O'Neill and Faulkner were stripped of effective leadership by a popular grassroots constituency revolt. This will not happen to David Trimble - there is no longer a popular grassroots constituency organisation of that type.

Nor is there any surge of support towards his political opponents within unionism: Union First is becalmed, as are both the DUP and the UKUP. Despite the prisoner releases, despite the negative impact of the Patten Commission project since the leak to this newspaper, morale is not high in the "No" unionist camp.

Indeed, relations between and within these groups remain uncertain. Union First does not want to be absorbed by a DUP/UKUP axis. The DUP fears the absolutism of the UKUP - expressed most recently in criticism of Peter Robinson's decision to attend a meeting in South Africa also attended by Sinn Fein.

Meanwhile, the UKUP is still afflicted by the doubts arising from Dr Conor Cruise O'Brien's opinions on Irish unity. The logic of any serious rejectionist position must include advocacy of withdrawal from Stormont and the refusal to take up ministerial positions. We can assume that this position is being advocated, but so far without many takers.

The agreement insists that each prospective minister must take a "Pledge of Office" committing him/ herself to exclusively peaceful and democratic means and to discharge all duties in good faith. Among those duties is the "essential responsibility" to participate in the North-South Ministerial Council. This has led some (in Sinn Fein particularly) to believe the DUP will be unable to take up its ministerial positions.

But paragraph 2 of (the Strand 2 section of the agreement) also states: "If a holder of a relevant post will not participate normally in the Council, the Taoiseach in the case of the Irish Government and the First and Deputy First Minister in the case of the NI administration to be able to make alternative arrangements". As things stand, it would appear that there is no insurmountable barrier to prevent the able Nigel Dodds, say, becoming Minister for Education.

This is a strange political battle; it is not being played by any recognised rules. Mr Trimble is not attempting to score a knockout blow against his unionist opponents - it cannot be done anyway. Rather, he is attempting - rather like Cosgrave in Dublin in the 1920s - to stay in power for long enough to force his rejectionists to accept the new constitutional rules of the game.

The prize is great: an end to the culture of despair and division within unionism. But his methods (rather like Cosgrave) are inelegant though not so brutal.

Mr Trimble needs to find a way of rallying his troops. There were signs this week in the US that he was finding his eloquent voice again. Today, he takes his share of the Nobel prize - a prize no doubt made all the sweeter by the characteristic generosity of some of Dublin's best-known nationalist commentators.

No doubt he will have serious things to say in Oslo. But it is Belfast where the battle has to be fought - it is in Belfast where the party has to be managed.

Paul Bew is professor of Irish politics at Queen's University Belfast.