Today Ukraine will be approved as a new member of the World Trade Organisation, the reward both for reforming its economy and for tilting towards the West rather than Russia.

The agreements to make it the WTO's 152nd member will not be signed until summer, but even so, it looks as though Ukraine has beaten Russia to the prize. The only countries bigger than Ukraine still outside the club are Russia and Iran, while the list of smaller ones consists of Libya, Kazakhstan and others of uncertain commitment to a market economy.

Today's ceremony, at the WTO's two-day general council in Geneva, shows that the trade organisation still has pulling power as a club that countries want to join — even though most of the world belongs. It can still persuade them to reform in order to join — in contrast, perhaps, to the European Union.

The greatest attraction to members is the leverage it gives them in settling trade disputes. President Yushchenko said that membership would give his country a stronger hand in negotiating with Russia over restrictions imposed on Ukrainian exports worth up to $3 billion.

The adjudication of disputes is also the part of the WTO that works fastest, usually producing a ruling within months. The hardest rows to resolve have been those between the EU and the US, about a fifth of the total. Officials say that there is little room for negotiation because each side arrives, equipped with some of the best legal advice in the world, clear on its rights and on what it wants. Yet, even in this unyielding area, predictions that the WTO would stall have proved wrong.

The WTO has found it harder to set trading rules in the first place, taking many years of anguish to do so — if it manages at all. Even so, the much-derided Doha Round, saved from the dead several times, may reach a conclusion this year. The stumbling blocks remain, as they have done for two years, subsidies and tariffs on farm products, and on services.

We are at a point when many international institutions set up after the Second World War are faltering. The World Bank and the International Monetary Fund, in particular, have been struggling to justify their existence in their old form, and are now challenged by the soveriegn wealth funds of Russia, China and oil-rich countries, anxious to find investment homes for their cash and less concerned about attaching conditions for good behaviour.

The WTO, just over a decade old in its present form, is not suffering from such an assault to its purpose. It has kept a long arm's length from the United Nations and that organisation's struggles to agree on action. It has been helped enormously by America's decision, generally, to support it, despite spouts of hostility from Congress when trade rulings go against the US. The US is also tempted perennially by bilateral deals where it would be in a stronger position to set the terms than it would within the WTO.

That the US chooses to stay in, where it is suspicious of the UN itself and ambivalent about other international organisations, shows the value the WTO offers to its members.

After Serbia's pro-European vote at the weekend, the EU is now confronted with the need to reward it. But while it holds out the chance of membership to countries to persuade them to reform, it has lost its appetite for awarding the prize at all — and potential candidates know it. In contrast, the WTO loses nothing by granting a membership countries will still go to some lengths to earn.

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