A 25-mile undersea tunnel linking Britain to the island of Ireland could be given the go-ahead next month.
The link, dubbed the 'Boris burrow', would connect Scotland to Northern Ireland.
Boris Johnson first backed the idea of connecting Larne in Northern Ireland to Stranraer in Scotland when he was foreign secretary in 2018.
However, his idea of a bridge has fallen out of favour as too complex and expensive, with a tunnel now seen as the preferred option.
It would be about 25 miles (40 kilometres) long and provide a road and rail link.
The secretary of state for Scotland Alister Jack reiterated his support for the link ahead of the expected release of a study that could kick off a formal consultation on the idea.
He said he had talked to the British Prime Minister and that a tunnel appeared the most viable way forward.
He told the Daily Telegraph's podcast: "You say bridge. I say tunnel. I think a bridge would be closed for probably 100 days a year with the weather in the Irish Sea."
He added: "My strong inclination would be that he [Mr Johnson] thinks it should be a tunnel because he and I have had conversations about the weather patterns in the Irish Sea and Beaufort's Dyke, and there's a munitions deposit there."
Any project would also have to avoid the dyke, a 30-mile trench up to 300m deep.
It is Britain's largest-known military dump, with the Ministry of Defence offloading around a million tons of munitions there between the 1940s and 1970s.
A report on UK transport infrastructure is reportedly imminent and expected to say the project is possible.
Additional reporting by IRN