LONDON – They call them the SIN countries, a wry acronym with faint undertones of disapproval. Pick up any map of the European Union and you'll spot them - defiant little white holes in the ever-widening yellow-and-blue EU livery stretching across the Continent.

Switzerland, Iceland, and Norway have been described as the lands that enlargement forgot, an unusual troika united only in their obdurate refusal to take up EU membership.

Yet now, with the EU expanding to take in 10 new countries and become the world's third-largest trading entity behind China and India, the risks of getting left behind are becoming more palpable, analysts say. "They are shooting themselves in the foot," says Katinka Barysch, an expert on EU enlargement with the Centre for European Reform.

Increasingly the SIN countries find themselves having to play by EU rules - without having any voice in how those rules are set, she says. "It is this position that previously drove countries like Sweden and Austria into the union."

The historic EU enlargement scheduled for May 1, taking in eight former Soviet bloc countries along with Cyprus and Malta, has provoked unprecedented debate. In London, battle lines are being drawn for a referendum on the new EU constitution, following a startling turnaround by Prime Minister Tony Blair last week in promising a national vote.

In central Europe, the focus is on jobs and the impact that enlargement and migration might have on unemployment. For new members, the debate turns on status and whether they truly are being accepted on an equal footing. And there is continued concern over economic disparities between East and West.

But in the SIN countries, it's a far more basic question: Do we stand more to lose by staying out than by joining? Thus far the answer has been a qualified "no."

The governments of Norway and Switzerland have both applied for membership in the past only to see the overture undermined by referendum results. Iceland has never put in an application. Though grouped together, the three countries are very different cases, and their reasons for not joining can be summed up in one word apiece. Norway: oil. Iceland: fish. Switzerland: neutrality.

Norway's oil has made it rich enough to pass up the economic benefits of EU membership. Yet now, like Iceland, Norway finds itself in a paradoxical position. Because the two are members of a small trade bloc called the European Economic Area (EEA), which participates in a single market with the EU, they are forced to adopt EU rules without having any voice in shaping them.

"Iceland and Norway take all the internal market legislation that the EU makes, but they don't have a say in that legislation," says Ben Jones, a Brussels-based expert and coauthor of a recent book on the SIN countries called "Forgotten Enlargement."

Thus the argument runs that a Pole or a Slovak or any EU national has more influence over legislation passed in Norway or Iceland than the electorate of those countries. Norwegians may be wising up to this: Latest polls show a majority in favor of joining.

For Bergdis Ellertsdottir of Iceland's Foreign Ministry, the young democracy's sovereignty is the biggest concern. Iceland has a population smaller than most US cities (at 300,000) and would be totally subsumed by the EU giant, she says.

And then there are the fish. Iceland almost went to war with Britain in 1975 over cod, so it is certainly not willing to hand control over to Brussels. And yet, polls show a 40:40 split in public opinion on joining, with 20 percent undecided.

Switzerland is a case apart, traditionally chary of international organizations (it joined the UN only two years ago) and historically fixated on its own neutrality, which dates back 350 years. But some note change in the air.

Recent spats with Germany over border controls and tax evasion matters have highlighted Switzerland's isolation. The government believes accession is in the Swiss national interest. And a poll earlier this month found two-thirds of people in favor of moving toward membership.

"Taking over EU law without having participated in the decisionmaking process is not very satisfactory," says Christian Meuwly, foreign ministry head of information. "The longer term aim of [our] European policy is to take Switzerland into the European Union."