Billionaire US presidential adviser Elon Musk said on Saturday he hoped Europe and the United States would agree to join in a free-trade zone after US leader Donald Trump unleashed heavy global trade tariffs.

Trump's sweeping tariffs announced earlier this week sent global stocks tumbling, worried allies, and raised the prospect of others – possibly the European Union – raising tariffs themselves.

The EU, which faces a 20 per cent tariff, has already vowed to retaliate in "a calm, carefully phased, unified way", EU trade chief Maros Sefcovic said.

"I hope that the United States and Europe can establish a very close partnership," Musk said in a video address to a gathering of the Italian hard-right party La Liga.

"I hope it is agreed that both Europe and the United States should move ideally, in my view, to a zero-tariff situation, effectively creating a free-trade zone between Europe and North America," he added in the video, posted on Musk's social media platform X by La Liga's leader, Deputy Prime Minister Matteo Salvini.

The billionaire said he favoured "more freedom for people to move between Europe and North America" for work.

"That has certainly been my advice to the president," he added.

But he reiterated his condemnation of what he saw as mass immigration. (AFP)