Elon Musk's electric carmaker Tesla has warned it and other US exporters could be harmed by countries retaliating to Donald Trump's trade tariffs.

Mr Musk is a close ally of the US president and is leading efforts to reduce the size of the federal government.

But in an unsigned letter addressed to the US trade representative, Tesla said while it "supports" fair trade it was concerned US exporters were "exposed to disproportionate impacts" if other countries retaliated to tariffs.

The letter was dated the same day that Trump hosted an event at the White House where he promised to buy a Tesla in a show of support for Mr Musk.

It is unclear who at Tesla wrote the letter as it is unsigned, or if Mr Musk was aware of it.

Tesla's share price has dropped 40% since the start of the year. Mr Musk is the carmaker's chief executive and while some have argued his alignment with the Trump administration is hurting its brand, market analysts say the share fall is more about worries over Tesla meeting production targets and a drop in sales over the past year.

In the letter, Tesla said it was making changes to its supply chains to find as many local suppliers for its cars and batteries so it was less reliant on foreign markets.

"None the less," it warned, "even with aggressive localisation of the supply chain, certain parts and components are difficult or impossible to source within the US."

The US president has imposed an additional 20% tariff on all imports from China, prompting Beijing to respond with retaliatory levies including on cars. China is Tesla's second biggest market after the US.

"For example, past trade actions by the United States have resulted in immediate reactions by the targeted countries, including increased tariffs on EVs imported into those countries," the letter reads.

The EU and Canada have both threatened sweeping retaliations for tariffs on steel and aluminium imports into the US, which went into effect earlier this week.