Support for the £4.4bn Fehmarnbelt scheme has increased in both Germany and Denmark, according to a poll.
Of more than 1,000 Danes questioned in March, 55% were positive about the prospect of a fixed link with Germany. This was up from 42% five years earlier.
In northern Germany, the proportion in favour of the scheme grew from 30% to 41% over the same period.
Nine teams last month handed in their tender documents to client Femern for four prestigious deals on the 19km tunnel project.
A spokesman for the client said this week: “We are, of course, grateful for the increasing support in both countries.
“There can be a number of explanations for the trend. As the project progresses, more people are becoming aware of the benefits that a fixed link across the Fehmarnbelt will mean for both Denmark and Germany.
“But the trend also indicates that there is growing confidence that we can undertake Europe’s largest construction project in a positive and justifiable manner.”
More than £30bn of construction work is expected to take place in Denmark between 2015 and 2021.