Washington DC - President Donald Trump said Friday that Iran has "no cards" in upcoming talks with the US – apart from Tehran's effective stranglehold on the crucial Strait of Hormuz shipping channel.

"The Iranians don't seem to realize they have no cards, other than a short term extortion of the World by using International Waterways," Trump said on his Truth Social network.

"The only reason they are alive today is to negotiate!"

In a separate social media message, the 79-year-old US leader added, "The Iranians are better at handling the Fake News Media, and 'Public Relations,' than they are at fighting!"

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Control of the narrow Strait of Hormuz, through which one-fifth of the world's crude oil passes, will be at the heart of peace talks between the US and Iran in Pakistan on Saturday.

Iran and the US said the crucial channel would reopen after a two-week truce was announced on Tuesday, but Tehran's threats mean very few ships are passing through.

Trump said on Thursday that Iran was doing a "very poor job" of allowing oil through the waterway, adding, "That is not the agreement we have!"

His "no cards" comments about Iran echoed his notorious broadside at Ukrainian President Volodymyr Zelensky in the Oval Office in February, when he raged that "you don't have the cards" against Russia.

Separately on Friday, Trump told the New York Post that US warships are being reloaded with weaponry to strike Iran if the talks fail to produce a deal.