Donald Trump’s visit will put “unquestionable pressure” on police forces across the country, according to an association that represents rank-and-file officers.
Almost all forces will send extra officers to help keep order at massive demonstrations planned in the capital and elsewhere during Mr Trump’s stay.
Forces are required to send officers for major events and emergencies outside their region under the mutual aid agreement.
Simon Kempton, operational policing lead for the Police Federation of England and Wales, said despite careful planning, the visit will still put a huge strain on law enforcement in some parts of the country.
He said: “Thousands of officers will be deployed from their home forces as part of mutual aid agreements, which are an important element of policing in this country to allow our resources to be flexibly and where they are needed most.
“However the fact cannot be ignored that while the officers on mutual aid are deployed elsewhere thousands more of their colleagues left behind in their home force will be expected to pick up the slack leaving them even more stretched.”
Though the US president will bring his own security detail, UK police will be expected to provide additional cover around his engagements and the protests, including the “Stop Trump” march planned for 13 July.
“There was a time when we could do it all but now choices have to be made,” said Mr Kempton.
“We cannot do it all and this type of event puts a service which is already creaking at its knees under unquestionable pressure.”
He said additional strain caused by the World Cup and the recent Novichok poisonings in Amesbury, Wiltshire, had reduced local policing to a “reactive service”.
Mr Kempton said: “You have to ask what would happen if were unable to resource incidents like these.
“Would we see the situation where the military were drafted in place of police officers? Green uniforms instead of the blue ones people would – and should – expect to see? It’s a worrying prospect.”
Even without a police presence, Mr Trump will likely be shielded from the worst of the protests set to take place, as his schedule ensures that he will spend most of his trip outside of London.
While thousands of people are expected to gather in central London to protest against the controversial president’s policies on matters including immigration and foreign policy, his UK government schedule means he will only spend one night in the city.
Activists were delighted when London mayor Sadiq Khan gave the green light to a gigantic balloon known as “Trump baby”, allowing them to fly it for two hours above Parliament Square Gardens on the morning of the protest.
Elsewhere, protests against the visit are set to take place across the country, everywhere from Belfast to York, and also at Blenheim Palace in Oxfordshire, where the president will be treated to a lavish dinner.
Additional reporting by PA.