There has been outraged reaction in Saudi Arabia to the case, which even the lawyers presenting it admit is not attempting to prove that any of the individuals named committed criminal acts. The case has been seen in the Arab world as being blatantly political and part of wider campaign to whip up anti-Saudi feeling in the US. The extent to which the case will in any way serve the victims of the Twin Towers attacks is open to question.

The choice of targets in the case betrays its essentially political content. Standing out in a distinguished crowd is Prince Sultan, Second Deputy Prime Minister and Minister of Defence & Aviation, full brother of King Fahd and widely seen as the second in line to the Saudi throne, and father of Prince Bandar, the Saudi ambassador to the US. Also named are Prince Turki al-Faisal, former head of the General Intelligence Directorate, and his brother Prince Mohammed al-Faisal, sons of the late King Faisal and brothers to Prince Saud al-Faisal, Saudi Arabia's Foreign Minister. The Kingdom of Saudi Arabia itself is not being sued, but by targeting such prominent individuals, the establishment is collectively under attack.

The institutions being sued are also heavyweights. Among them are two of the largest banks in Saudi Arabia - the National Commercial Bank and Al-Rajhi Banking & Investment Corporation - the Dallah Albaraka Group and Dar al-Maal al-Islami (see box).

In more simplistic fashion, the Republic of Sudan is also being sued.

On a practical basis, the case is fanciful. The worth of the $100 trillion price tag attached to the case against Sudan can be measured against the country's gross domestic product of less than $12 billion. Equally implausible is the likelihood of any ruling being effectively enforced against the Saudi defendants.

However, the civil action does have sizeable ramifications. 'As US-Saudi relations have clearly become increasingly strained, this is another straw on the camel's back,' says Raad Alkadiri of the Washington-based Petroleum Finance Corporation. 'This may not be the straw that breaks the back, but the camel is looking increasingly uncomfortable.'

It is too early to assess the full impact of the case, but there are a number of important stages that will determine the extent of the escalation. First, the defendants will decide whether to defend themselves vigorously or take the risk of ignoring proceedings. The likelihood is that powerful legal teams will be rapidly assembled and that they will look to go on the offensive as quickly as possible: motions to dismiss the case will probably be filed in bulk. If the sitting judge deems the case worth hearing, the discovery process will begin - it could take up to a year, according to the plaintiffs' lawyers - and if the evidence appears strong enough motions will begin. The plaintiffs' lawyers say a case management conference will be held 'before long' in which the judge will outline a timetable for the proceedings.

Big political issues will soon start presenting themselves to the US administration. 'The interesting point is whether the State Department decides to submit a document to the court supporting a motion to dismiss,' says a Washington-based lawyer with extensive experience of Saudi-US relations. 'This has happened a lot in previous cases involving Saudi Arabians in US courts.' It might have been normal in the past, but this case is far from being routine and the State Department will be only too aware of the sensitivity of the issue and the dilemma it faces. To testify in the motions for dismissal is to risk the wrath of public opinion still seeking satisfaction for the 11 September attacks. Do nothing, and relations with Saudi Arabia could be irrevocably damaged.

The Bush administration has a problem. While the State Department has been consistently asserting that relations with its oldest ally in the Middle East are as robust as ever, the record is wearing thin and the civil case could further open an apparent policy schism. And that might be one of its objectives.

'We are not working closely with the State Department at present,' says Allan Gerson, a Washington-based attorneys representing the plaintiffs. 'But we have received support from US national security officials. They believe that the discovery process could be very important.' While the full extent of this 'support' remains opaque, such an acknowledgement stands as another wedge driven into the administration.

The political nature of the attack is underscored by the composition of the list of defendants. 'We are able to sue the Republic of Sudan because of the [1996] Anti-Terrorism Claims Act,' says Amy DeBrota, another of the lawyers representing the plaintiffs. As Sudan is listed in the annual State Department report as a sponsor of international terrorism it is denied access to sovereign immunity: Saudi Arabia is not a state sponsor of terrorism. 'This is one of the reasons why we have not sued Saudi Arabia, just members of the Saudi government,' says DeBrota.

One school of thought in Washington suggests the civil suit has multiple objectives. Freezing the funds that fuel terrorism might be the public aim, but forcing a radical rethink of regional policy might not lie far from the surface. The neo-conservative aim of diluting Saudi Arabia's importance as a regional ally and the more robust application of perceived US national interests could be promoted. As could the liberal democrats' agenda which focuses on Saudi Arabia's human and civil rights record. Washington analysts see neo-conservative fingerprints: the case filed directly quotes passages from the notorious 10 July Pentagon briefing given by the Rand Corporation's Laurent Murawiec.

'This is another nail in the anti-Saudi edifice that minority interests in the US are attempting to construct,' says Greg Gause, Professor of Political Science at the University of Vermont. 'But the debate continues to be stronger outside the administration than within it.'

Whether the edifice will be completed remains to be seen and will, in part, be determined by the unfolding of US policy on - and events in - Iraq and Palestine. Perhaps more importantly, the stimulus for change might come from Saudi Arabia itself. Improved relations with Iran and a more active approach to regional issues have become the norm in recent years. The civil suit might further encourage a rethinking of the old US alignment.

The case for compensation may be a bold one, but it is not the first. The families of the victims of Pan Am 103 continue to seek redress from the Libyan government of Muammar Gaddafi - in May an informal offer of $10 million for the families of each of the 270 victims was tabled - but the process has been politicised. The UN and the US have both attached key conditions to the raising of sanctions imposed on Libya: Tripoli must renounce terrorism; it must pay appropriate compensation; it must disclose information relating to its involvement in international terrorism; and it must accept responsibility. The first condition has been met, the second is being pursued, the third is academic, but the fourth continues to be an insurmountable barrier. Gaddafi too has a political agenda and there are few signs that conceding responsibility for the 1988 Lockerbie bombing is on it.

If the process is mirrored in the 11 September case - which in many aspects is considerably less straightforward, not least because the civil action precedes government moves - the plaintiffs could be in for a protracted, painful wait.

However, the 11 September case itself is comparatively simple. 'The causal chain is that the defendants knew that money they provided would be partly used to fund terrorist activities targeting the US,' says Gerson. 'This is not a criminal case: we only have to prove - in the balance of probability - that the defendants had good reason to know that the money they gave would be used to fund terrorism. We don't have to prove that they had any detailed knowledge of any particular plans.'

The 259-page document filed with the court reflects the generalised nature of the case. It is long on assertion and makes little attempt at detailed substantiation of the allegations against the defendants.

Whatever course the case takes it will still have an impact, and not only on the growing tension between Riyadh and Washington. The flow of Arab capital in and out of US markets is likely to be altered. Estimates of the value of Saudi investment in the US vary wildly from $500,000 million to figures as much as three times higher. Whatever the real total is, it is fair to assume that it will fall over the next few months.

'The whole process is unacceptable and this will only lead to an acceleration of the trend in which Arab investors are liquidating US investments,' says a senior banker in Riyadh. 'There is now a perceived risk as the US has demonstrated a willingness to ignore the law and work outside due process. Since 11 September assets have been frozen, people have been declared terrorists, prisoners have been held, all without trial. The changed attitude in the US will bring a change in attitude among Arab investors in the US.'

So far, there have been no attempts made by the plaintiffs to freeze the defendants' assets, though it remains an option. 'No decision has yet been taken on this yet, but it will be soon,' says DeBrota.

It is likely to be considerably longer before a decision can be taken over whether the civil proceedings can be deemed a success. 'Our clients know they are fighting an uphill battle but their primary objective is to starve terrorism of the finance it needs and to focus attention on who is responsible,' says DeBrota. 'Their secondary goal is compensation.'

And here lies perhaps the most bitter irony of this extraordinary case. A decision is expected soon over whether the plaintiffs will - by pursuing the civil action - be waiving their rights to US government compensation. With their lawyers working on a no-win-no-fee basis there is a strong possibility that the action could end up costing the plaintiffs and their lawyers more dearly than the accused.