LONDON, Jan. 19 (Xinhua) -- Britain's foreign secretary Boris Johnson has called for Britain and France to be linked by a road bridge.

Johnson discussed the idea with French President Emmanuel Macron during a British-French summit Thursday. At its narrowest point, the bridge would need to be at least 34 kilometers long, not counting approach roads, according to media reports.

Ian Firth, senior vice president at the Institution of Structural Engineers, said on his social media site: "A bridge is entirely feasible. It was a serious contender to the (Channel) tunnel and is even more feasible now. Costly, yes, but so was the tunnel."

Firth said combining a bridge with a tunnel could avoid any impact on shipping in what is one of the world's busiest seaways.

Sea journeys between Britain and mainland Europe were possible until 1994 when the 50-kilometer Channel Tunnel opened, but that is only a rail tunnel.

Johnson described as ridiculous that only a rail tunnel linked the two countries. Sources at the meeting said Macron responded positively to Johnson's idea.

Thailand-born civil engineer Sakdirat Kaewunruen, a senior lecturer at the University of Birmingham, said a bridge across the English Channel would be a challenging and difficult, but exciting project.

He told Xinhua: "I am very supportive of such a project. It could be a multi-purpose bridge carrying road traffic, trains and even used to generate energy from wind power."

"There would be hazards and climate change to consider, but such a project would create new expertise in bridge building. It would be a massive boost to the economy."

Files released by Britain's National Archives reveal plans were put forward in 1981 for a bridge spanning the English Channel, at a then cost of around three billion pounds.