Sir Keir Starmer has called the move “completely wrong” and said his government would be “pursuing this directly with the US administration”.
The White House has in recent weeks intensified calls for a US takeover of the autonomous Danish territory, which Trump says is critical for US security. He has not ruled out taking it by force.
The plan would see a 10% tariff on goods from Denmark, Norway, Sweden, France, Germany, the UK, the Netherlands and Finland from 1 February, which could later rise to 25%, until a deal was struck for a US takeover of Greenland.
Nandy said Trump will often “express a very strong view” before encouraging “dialogue”.
“He welcomes difference of opinion… and what often happens is a negotiation,” she said.
Asked whether she believed Trump would row back on the tariffs, Nandy said: “I think this is actually a really serious issue, and I think it deserves a far more adult debate than us threatening the United States, and the United States threatening us.”
“The one thing that we won’t do is compromise on our position” that Greenland’s future was for its people to decide, she added.
“That is non-negotiable. That is the starting point for the conversation.”
US House Speaker Mike Johnson told Laura Kuenssberg before the tariffs were announced that he accepted Greenland was “not our land” but that it had “strategic importance to us”.
“I don’t foresee military intervention”, he said. “I think diplomatic channels is the way to go”.