President Jacques Chirac inaugurated the world's highest bridge yesterday, a creation taller than the Eiffel Tower, longer than the Champs Elysees and designed to end a traffic bottleneck in southern France.

Conceived by British architect Norman Foster, the slender white viaduct in the picturesque Tarn Valley will provide a new motorway link between Paris and the Spanish border, easing congestion in the Rhone valley during the busy summer months.

Chirac unveiled a simple commemorative plaque before plunging into a throng of white helmeted construction workers, as an air display team flew past the bridge trailing red, white and blue smoke - the colours of the national flag.

He hailed the viaduct as a "marvel of art and architecture", a monument to French engineering genius that was a "miracle of equilibrium" and projected a bold, successful, modern image.

"The Millau Viaduct is a magnificent example, in the long and great French tradition, of audacious works of art, a tradition begun at the turn of the 19th and 20th centuries by the great Gustave Eiffel," Mr Chirac told a reception.

The highest of the bridge's seven concrete pillars stands at 343 metres, 19 metres higher than the Eiffel Tower. At almost 2.5 km, it is longer than the Champs Elysees and slightly curved to afford drivers a dramatic view of the surrounding countryside and the ancient town of Millau with its mediaeval bell tower.

"The whole thing looks impossibly delicate," Foster said in a telephone interview of what he called his "sculpture in the landscape", a 394-million-euro project financed by construction firm Eiffage.

"It is a dialogue between nature and the man-made," he said.

The engineering feat has drawn rapturous praise for its elegant lines, which allow it to blend seamlessly into the surrounding region famed for its gorges, mediaeval villages and Roquefort cheese.

"We were attracted by the elegance and logic of a structure that would march across the heroic landscape and in the most minimal way connect one plateau to the other," said Foster, who designed the glass dome that tops Germany's Reichstag parliament building in Berlin.

"We were driven by the scale of the idea and the shared passion for the poetic dimension of engineering and its sculptural potential," he said in a statement.

The Millau viaduct has drawn thousands of visitors since construction was started exactly three years ago.