"The European continent deserves to be free from any aggression, but it ought be those in the neighbourhood investing the most" in its defence, he said at a US base in Germany.

On the first stop of a Europe trip, the senior member of US President Donald Trump's administration said he planned to have "straight talk with our friends".

He is also set to meet NATO defence ministers, attend a gathering of Ukraine's international supporters in Belgium, and make a visit to Poland for talks with its leaders.

The "urgency of this moment requires friends talking to friends about capabilities, about leadership, about stepping up, about burden sharing," he said during a live-streamed press conference at a US military facility in the southwestern city of Stuttgart.

He repeated Trump's demand for NATO countries to ramp up defence spending to five percent of GDP, more than double the current target, saying it was a "reflection of a need to invest on the continent".

Few in Europe however see this figure as feasible.

Hegseth also reiterated that Trump had promised to deliver "a rapid peace deal in Ukraine", a stance that has provoked fears Kyiv could be forced into making a one-sided deal with Russia.

When asked whether the US would be willing to send its armed forces to Ukraine, he responded: "We're not sending US troops to Ukraine."

He added that Washington planned to review "force posture across the world", and repeatedly singled out China as a major threat to the United States.

Beijing's "intentions are pernicious" and Washington will have to focus "properly on the Communist Chinese and their ambitions in the Indo-Pacific", he said.

But he also insisted that "We don't want conflict with China".