Shares of Dublin-based packaging group Smurfit Kappa plunged 11% at Tuesday’s market open in London after it announced it would combine with U.S. peer WestRock to create an industry juggernaut.

The companies will form Smurfit WestRock — set to be one of the largest packaging companies in the world — run through a holding company incorporated and domiciled in Ireland.

It will seek a New York listing with a standard listing on the London Stock Exchange.

WestRock shareholders will receive one Smurfit WestRock share and $5 cash, equivalent to $43.51 per share.

“We’ve always said we had a very big gap in our portfolio because we were not involved in the United States. We’ve been looking over many years to figure out a way to get in there in a way that would reward our shareholders over the long term,” Smurfit Kappa CEO Tony Smurfit, who will lead the combined company, told CNBC’s “Squawk Box Europe.”

“We identified [Westrock] as an asset that we can develop with and combine with to be an even better asset. So after a series of negotiations, we finally got to an agreement at 7:15 [a.m. London time] this morning to finally close out this deal, which I think is going to be fantastic for our shareholders in the long-term, medium and short-term.”

This is a developing story and will be updated shortly.