Iran may have agreed to a ceasefire in the Middle East, but it won’t soon forget the humiliation it suffered at the hands of the US over the weekend.

Senior figures in Donald Trump’s administration have warned the country is at risk of an attack by secret agents operating in “sleeper cells”, after the US president bombed Iran’s nuclear facilities early on Sunday morning.

The term “sleeper cell” refers to covert agents or terrorists who operate undetected within a rival country, blending into the background until being given an order to act.

So as tensions in the Middle East seemingly cool down, the US remains on high alert.

Experts warn Iran will have taken advantage of the lax approach to border security under Mr Trump’s predecessors to smuggle in individuals primed to inflict chaos.

Once they have assimilated themselves in the population, they seek to build networks, either with fellow Iranians or criminal associates, before targeting critical infrastructure, fomenting unrest or launching attacks.

En route to the Nato summit on Tuesday, Mr Trump claimed that Joe Biden, the former US president, had endangered national security by failing to stop illegal border crossings.

“Biden let a lot of super cells in,” he said, apparently referring to sleeper cells, “He let a lot of super cells in, many from Iran. But hopefully we’ll take care of them.”