Washington DC - President Donald Trump claimed that a potential Supreme Court ruling against his power to apply tariffs would threaten national security.

Since November 5, the court has been examining the legality of Trump's sweeping tariff policy, although no date has been set for a ruling.

Several businesses and Democratic-led states have also filed complaints with the US Court of International Trade, arguing that the tariffs are unconstitutional as the power to impose them rests with Congress.

"The biggest threat in history to United States National Security would be a negative decision on Tariffs by the US Supreme Court," Trump said on social media.

The US would be "financially defenseless" if the Supreme Court ruled against him, he claimed, adding: "We would not be allowed to do what others already do!"

Trump also included a photo of French President Emmanuel Macron during his visit to China last week in the Truth Social post.

On Sunday, Macron threatened China with tariffs "in the coming months" if Beijing fails to take steps to reduce its massive trade surplus with the European Union.

In a second post, Trump wrote: "Because of Tariffs, easily and quickly applied, our National Security has been greatly enhanced, and we have become the financially strongest Country, by far, anywhere in the World. Only dark and sinister forces would want to see that end!!!"

Trump's approval ratings have slumped to their lowest point since his return to office in January, particularly over the cost of living, blamed at least partly on tariffs. US inflation accelerated in September to 2.8%.

The issue has also caused a rift within the MAGA movement. Former close ally Marjorie Taylor Greene, who broke with Trump in November and will resign her congressional seat in January, said the president had failed to focus on affordability.

Last week, Costco became the largest US company to challenge Trump's tariff regime, which it claims are illegal.