Isis has used a 10-year-old American boy to issue a threat to Donald Trump as the group seeks to inspire terror attacks around the world.

The boy, named in the propaganda video as Yusuf, appeared in footage Isis claimed was filmed in its de-facto capital of Raqqa, which is surrounded by advancing US-backed forces.

“My message to Trump, the puppet of the Jews,” he said, staring into the camera.

“Allah has promised this victory and he has promised you defeat. This battle is not going to end in Raqqa or Mosul, it is going to end in your lands.

“By the law of Allah we will have victory, so get ready for the fighting has just begun.”

Appearing to be reading from a script, Yusuf said he moved to the so-called Islamic State two years ago from the US with his mother, and claimed his father was an American soldier who had served in Iraq.

He called his home country a state of “non-believers” and claimed Isis had “established the rule of Allah”.

A 10-year-old American boy named as Yusuf in an Isis propaganda video released in August 2017

The seven-minute-long propaganda video showed Yusuf reading the Quran, wandering through rubble, in a mosque and playing with his “best friend” Abdullah – said to be a Yazidi boy kidnapped by Isis during its genocide in Sinjar.

They are among thousands of children trapped in Raqqa, according to Unicef figures, as the besieged city is bombed by the US-led coalition and advancing troops.

Isis frequently publishes gory images claiming to show alleged massacres by coalition bombing, which Yusuf said happens “every night”.

The footage, which could not be independently verified, showed militants preparing for the offensive by making tunnels, strapping on suicide vests and picking up guns amid the sound of gunfire and bombardment.

It ended with Yusuf and seven-year-old Abdullah driving a hole in a wall before an older fighter apparently trained the American boy to use a sniper rifle.

“Do you think that we’ll be finished?” Yusuf said. “Never! We will remain until the day of judgement.”

The group has featured the children of foreign fighters prominently in propaganda videos, using boys believed to be the sons of British Isis members Sally Jones and Grace “Khadija” Dare in gory executions.

Several British members are believed to have had children in Syria, including Abu Rumaysah – real name Siddhartha Dhar – who posted a photo of his newborn son on Twitter and called him a “great addition to the Islamic State”.

The latest threat comes as Isis turns its attention from building a “caliphate” in waning territories in Syria and Iraq to inspiring global insurgency and terror.

A 10-year-old American boy named as Yusuf and seven-year-old Yazidi boy in an Isis propaganda video released in August 2017

Nikita Malik, a senior research fellow at the Henry Jackson Society, said leaders were attempting to threaten the West with a “new generation” of brainwashed jihadis.

“They’re doing it because they can, because they want to show what they’re capable of,” she told The Independent.

“There used to be a lot of propaganda of children in school or running around in playgrounds, kind of showing a utopia, but now it’s very much saying ‘we have a new generation of fighters and they’re coming for you’.”

Ms Malik said the darkest Isis propaganda has always come out of territory under threat and the latest “disturbing” video was no exception.

“Children make great props for a terrorist organisation but the deeper message is that ‘our losses don’t matter because... look at how dangerous these children are’,” she added.

“There is a danger that the ‘state’ Isis created will be romanticised and the people who will seek to replicate it is these children who have been indoctrinated.”

European security services have warned of the danger of returning Isis members amid questions over how children will be de-radicalised and reintroduced to Western society.

A report on terror threats to the EU released by Europol last month noted that women and children were “playing increasingly operational roles” in terror plots, which have intensified as the number of extremists able to travel to Iraq and Syria plummets.

“The number of returnees is expected to rise if Isis, as seems likely, is defeated militarily or collapses,” Europol said.

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“An increasing number of returnees will likely strengthen domestic jihadist movements and consequently magnify the threat they pose to the EU.”

The report noted that Isis propaganda “has repeatedly depicted the training and indoctrination of minors” and said anyone subjected to prolonged ideological indoctrination and military training presented a threat.

At least 80 British children were believed to be living in Isis territory at the latest count, although an unknown number are likely to have died in military offensives.

Isis has hailed the children of its fighters as the next generation of the so-called Islamic State, using teenagers as suicide bombers and fighters while deploying younger children to carry out executions in propaganda videos.

Leaks from its territories have revealed a gruesome curriculum where boys are forced into terror training camps or jihadi schools to be indoctrinated in Isis ideology and desensitised to violence using “homework”, which includes beheading dolls.

The group even released its own education app last year, using guns, tanks and swords to illustrate an alphabet set to an extremist nasheed (song).

Shiraz Maher, deputy director of the International Centre for the Study of Radicalisation (ICSR) at King’s College London, said Isis is attempting to create a “generational war”.

“There are huge implications as to what happens in the future,” he told The Independent.

“No one really knows how many children Isis has but it’s a lot, and there are very young children out there who are incredibly vulnerable and about whom there’s no legal jurisdiction.”

US backed fighters make progress in driving Isis out of Raqqa

The Syrian Democratic Forces (SDF) are screening civilians escaping Raqqa as they advance but the treatment of children is unclear, with many of those born under the so-called Islamic State expected to be stateless.

“Clearly these are deeply damaged children who will have seen horrific things,” Dr Maher said.

“Groups elsewhere have been reticent to admit they use child soldiers but Isis gives them a prime place in propaganda... it has has sought to affront humanity and the international order.

“These children could die or they will be captured, it’s a pretty grim existence. It’s industrial scale child abuse... their lives have been completely shaped and developed inside this insane project.”

Dr Maher said the fighters choosing to remain in Raqqa are among the “most militant” of all Isis supporters and few are expected to survive – an expectation echoed by American commanders and humanitarian groups.

Unicef warned that heavy fighting in Raqqa and the Isis stronghold of Deir ez-Zor was having a “staggering” impact on children who must be protected under international law.

“According to reports Unicef is receiving from inside Raqqa city, several thousand children continue to be trapped in the city, caught in the direct line of fire,” said Fran Equiza, the agency’s representative in Syria.

“With no access for humanitarian agencies, the city is completely cut off from lifesaving assistance. Children and families have little or no safe water while food supplies are running out fast.

“Children and families who wish to leave Raqqa city must be allowed to do so in safety and in dignity.