A new propaganda video featuring the British hostage John Cantlie has been posted online by Islamic State (Isis) within hours of the launch of US-led air strikes against the group in Syria.

Appearing once again behind a desk and reading calmly from a script, Cantlie used the latest in what he says will be a series of “programmes” to condemn the military build-up in the region.

In a previous video posted by the group, the freelance photographer – who has been a prisoner of Isis for 22 months – made clear that he was making the films under duress.

In the latest 5min 45sec video, Cantlie warns that the US and its allies were embarking upon what he describes as “Gulf War III”, adding: “Not since Vietnam have we witnessed such a potential mess in the making.”

His references to UK military aid to Kurdish forces and French and Danish support for military action suggest that the video was made in recent days. Other aspects of the film, such as his stubble and the state of the orange jumpsuit in which he is dressed, suggest that it may have been made at the same time as the last video in which he featured.

Against a backdrop showing cuttings from the New York Times, Cantlie, 43, introduces himself as “the British citizen abandoned my government, and long-term prisoner of the Islamic State”.

He then quotes former CIA officer and critic of US intervention in Iraq Michael Scheuer: “Eighteen years into our war with the Islamists, the US government has given no public sign that it has the slightest awareness of what its enemies are fighting for.”

Cantlie goes on: “Senior US politicians seemed content to call the Islamic State nasty names; ‘awful’, ‘vile’, ‘a cancer’, ‘an insult to our values’. But such petty insults don’t really do much harm to the most powerful jihadi movement seen in recent history.

AN image from the previous Islamic State video of captured British photojournalist John Cantlie. Photograph: Rex Features

“The president once called George Bush’s conflict a dumb war and couldn’t wait to distance America from it when he came into power. Now he’s been inexorably drawn back in, but he’s at pains to point out that this is not the equivalent of the Iraq war. Indeed it’s far more complicated and prone to failure.”

At the end of the film, Cantlie warns, on behalf of his captors, against military operations on the ground against Isis: “Current estimates of 15,000 troops needed to fight the Islamic state are laughably low,” he says. “The State has more mujahideen than this. And this is not some undisciplined outfit with a few Kalashnikovs.”

He then says there will be a further “programme” posted on the internet.

There was no immediate reaction from British government officials or ministers.

Cantlie was kidnapped in November 2012 along with the US photographer James Foley, whose murder was filmed by Isis and posted online last month.

It was the second time Cantlie had been abducted in Syria: earlier that year he was held for seven days before being freed by a rival opposition group.

There has been no mention in either of Cantlie’s films about the other western hostages held by Isis. They are thought to number more than a dozen, and include Alan Henning, 47, a taxi driver from Greater Manchester who was kidnapped last December after volunteering to join his Muslim friends on an aid convoy to Syria.

Muslim clerics around the world have been appealing for the release of Henning after he was shown in a previous Isis video, which also depicted the murder of Scottish aid worker David Haines.