It has been one of the elusive goals of seafaring nations almost since the beginnings of waterborne trade, but for nearly 500 years the idea has been dismissed as an impossible dream. Now, as a result of global warming, the dream is about to come true.

Within days, a journey that represents both a huge commercial boon and a dark milestone on the route to environmental catastrophe is expected to be completed for the first time. No commercial vessel has ever successfully travelled the North-east Passage, a fabled Arctic Sea route that links the Atlantic Ocean and the Pacific far more directly than the usual southerly cargo route. Explorers throughout history have tried, and failed; some have died in the attempt.

But early next week the German-owned vessels, Beluga Fraternity and Beluga Foresight, are scheduled to dock in the Dutch port of Rotterdam. It is the culmination of a two-month voyage from South Korea across the perilous waters of the Arctic, where an unprecedented ice-melt has at last made the previously impassable course a viable possibility.

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The new route could transform Russia's economic fortunes. Throughout history, the country's search for a warm-water port that would provide sea routes open year-round has dominated the geopolitics of the region. But the economic advantages are balanced by the disastrous environmental news that the transit represents.

"This is further proof that climate change is happening now," said Melanie Duchin, Arctic Expedition leader on board the Greenpeace ship Arctic Sunrise, who added that the development put greater pressure on world leaders to agree a major emissions cut at their Copenhagen meeting in December. "This is not a cause for celebration but cause for immediate action," she said.

The 12,000-tonne vessels' summer journey through the Northeast Passage was carried out with 3,500 tonnes of construction materials and parts for a Siberian power station on board. Once completed, the voyage will have shortened the traditional commercial sea route from the Far East to Europe – via the Suez Canal – by more than 4,000 nautical miles.

Russian maritime officials are now hoping that the feat will result in an "Arctic Rush" with the northern sea route becoming a viable summer competitor to the Suez and Panama canals. They have offered to cut ice-breaker fees in the North-east Passage to encourage major shipping companies to start using it.

Nils Stolberg, the President of the Bremen-based Beluga group which organised the commercial voyage insisted yesterday that ships' transit was not an experiment but the first step towards opening the North-east Passage to shipping world wide. He said his company already had new contracts to ship goods along the route from Asia to Siberia next summer.

"We are all very proud and delighted to be the first Western shipping company to have successfully transited the legendary North-east Passage and delivered a sensitive cargo safely through this extraordinarily demanding sea area," he said. He also estimated that the path had saved $92,000 (£55,000) worth of fuel for each ship.

Despite global warming, the Northeast Passage is still seriously hampered by hundred-mile long swathes of shifting pack ice that extend southwards from the North Pole even in summer. The islands off the north coast of Siberia also contain glaciers which cast icebergs into the warming waters of the passage with increasing frequency.

In 1983 a Russian ship was crushed by pack ice it encountered in the passage in the middle of summer. However, the Russian Transport Ministry which operates a fleet of six nuclear powered-ice-breakers to assist Russian and other coastal commercial ships, says that in recent summers the route has rarely been completely impassable. "The ice conditions were far more severe 20 years ago," a spokesman said.

The voyage of the two Beluga vessels was certainly no picnic. Although not thoroughbred ice-breakers themselves, both ships were designed to cope with ice-strewn waters and were accompanied by at least one Russian nuclear ice-breaker during the whole of the trip. The two ships encountered snow, fog, ice floes, and treacherous icebergs which showed only about one meter of their huge underwater volume on the sea's surface.

The most challenging stretch of the voyage came at its northernmost point, the Vilkizi Strait on the tip of Siberia. Half of the sea's surface was covered with pack ice and the captains of both vessels had to call Russian ice pilots on board to shepherd them through. Vlarey Durov, captain of the Beluga Foresight spoke of the stress he experienced from having to keep a constant lookout for ice and the time spent waiting for the seas to clear. But he insisted: "It is an economically and ecologically beneficial shortcut between Europe and Asia... On such voyages the advantage of fewer miles can outweigh the delays in waiting for clear water."

Finding a North-east Passage from the Atlantic to the Pacific was the goal of mariners and governments in 16th-century Europe because the route would have shortened the voyage to the newly discovered spice islands of the East Indies by some 2,000 miles – the equivalent of a year's sailing.

However, most expeditions ended in disaster. The first attempt by the British navigator Richard Chancellor took place in 1553 but was brought to an abrupt halt in the winter of the same year when his ships became trapped in the ice. Chancellor abandoned ship and marched across the ice to Moscow where he was entertained at the court of Ivan the Terrible.

His fellow explorer Sir Hugh Willoughby stayed with his crew aboard ship and was discovered frozen to death two years later.

Another attempt in 1597 by the Dutch explorer William Barents ended with his ship being trapped and crushed in the ice. Barents and his crew were forced to spend the winter in a makeshift driftwood hut living on polar bear meat. Barents, after whom the polar Barents sea is named, did not survive either.

If the current voyage ends successfully, such maritime disasters may become a thing of the past. But a separate environmental disaster may be only beginning to unfold.