BERLIN (Reuters) - Europe wants to cooperate with the United States but the EU is ready to respond as one if Washington leaves it no choice by imposing tariffs on steel and aluminium, German Chancellor Olaf Scholz said on Sunday.

Speaking at the opening of the Hanover industrial trade fair which this year has Canada as its partner country, Scholz also insisted that Canada is an independent country.

U.S. President Donald Trump has mused about annexing Canada and referred to the country as the 51st U.S. state.

"We stand by your side!" Scholz said, adding: "Canada is not a state that belongs to anyone else. Canada is a proud, independent nation."

Addressing Trump's plans to introduce tariffs, Scholz said his answer to "my country first" policies was more free trade, greater competitiveness and more technological sovereignty.

Scholz argued that Europe was not naive but also not weak, and said trade wars hurt all sides.

"So I say to the United States: Europe's goal remains cooperation. But if the U.S. leaves us no choice, such as with the tariffs on steel and aluminium, we as the EU will react as one".

(Reporting by Andreas Rinke; Writing by Madeline Chambers; Editing by Thomas Seythal)