For centuries the Danube has been a vital international trade artery through Central and Eastern Europe, interrupted only by the second world war. But its bridges have been a consistent target of Nato action against Serbia, effectively blocking the river.
Frank Worsford, an expert on freight and distribution at Westminster University's transport studies group, believes the effect could be "catastrophic". "As these countries' infrastructure is not as advanced as in the rest of Europe, they are more dependent on the river network for the carriage of essential bulk goods. If the Danube is blocked, the effect on those economies dependent on this flow of goods would be felt immediately I Industry will grind to a halt."
Three of the most directly affected - Bulgaria, Romania and Slovakia - are applicants for European Union membership and the long-term health of their economies is a vital criterion for a successful result. A two-year EU-led research project into the future of the Danube as a key part of the transport infrastructure was specifically charged with taking into account the situation in the former Yugoslavia and the further integration of Eastern European countries.
However, Roger Vickerman, Jean Monnet professor of European economics and director of the Centre for European, Regional and Transport Economics at the University of Kent, thinks the impact is likely to be "important but not devastating".
"The Danube would affect particular types of traffic to particular markets. Bulky low-value goods would be affected most. For Hungary and Slovakia there is less of a problem since they would be looking to western markets that are not affected. They are more developed than Romania and Bulgaria, which would be affected by their inability to transport agricultural and raw-material products upstream.
"However, these countries are all looking to develop in newer industries which would be less likely to use the Danube as a mode of transport. This is an inconvenience which is not life-threatening for these economies, though it might affect individual firms and regions rather more.
"For most there are alternatives, eg rail I though this has environmental consequences."