A senior Iranian official has warned that the country will treat any attack "as an all-out war against us" ahead of the arrival of a US aircraft carrier strike group and other assets in the region.

The warning and surge in US military presence comes almost two weeks after Donald Trump urged Iranian protesters - thousands of whom have been killed by the regime's forces - to keep demonstrating and promised that "help is on the way".

"This military ‌build-up - we hope it is ‌not intended for real confrontation - but our military is ready for the worst-case scenario. This is why everything is on high alert in Iran," said the Iranian official, speaking ‌to Reuters on condition of ⁠anonymity.

The official went on to say: "This time we will treat any attack - limited, unlimited, surgical, kinetic, whatever they call it - as an all-out war against us, and we will respond in the hardest way possible to settle this."

Mr Trump said on Thursday that the US had an "armada" heading toward Iran but hoped he would not have to use it, as he renewed warnings to Tehran against killing protesters or restarting its nuclear programme.

"If the Americans violate Iran's sovereignty and territorial integrity, we will respond," said the Iranian official.

He declined to specify ‌what an Iranian response might look like.

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The US military has periodically sent additional forces to the Middle East at times of heightened tension, moves often seen as defensive.

However, the US military staged a major build-up last year ahead of its launching airstrikes against Iran's nuclear programme in June.

Another build-up was seen in the Caribbean towards the end of last year before the US launched military action against Venezuela and captured the country's president Nicolas Maduro.

'Iran may try again to obtain nuclear weapon'

Meanwhile, the Pentagon has published a new national defence strategy, which included analysis on Iran.

The document warned Iran may attempt to obtain a nuclear weapon, something it has accused Tehran's leaders of attempting before.

The document also said Iran had "the blood of Americans on its hands" and pledged US support for Israel.

It read: "Although Iran has suffered severe setbacks over recent months, it appears intent on reconstituting its conventional military forces.

"Iran's leaders have also left open the possibility that they will try again to obtain a nuclear weapon, including by refusing to engage in meaningful negotiations."

It added: "Nor can we ignore the facts that the Iranian regime has the blood of Americans on its hands."

The document stated Iran "remains intent on destroying our close ally Israel, and that Iran and its proxies routinely instigate regional crises that not only threaten the lives of American servicemembers in the region but also prevent the region itself from pursuing the kind of peaceful and prosperous future that so many of its leaders and peoples clearly wish for".