The PSNI has asked for 330 officers from the rest of the UK to assist with a massive security operation during a visit to Northern Ireland by US President Joe Biden.
Mr Biden has confirmed he will visit Northern Ireland and the Republic as part of the celebrations around the 25th anniversary of the Good Friday Agreement next month.
Assistant Chief Constable Chris Todd said that while there was no confirmed date for the presidential visit, the police service would have contingencies in place.
He said: “We have asked for approximately 330 officers from across the United Kingdom to support the policing operation.
“The mutual aid officers will be used to provide additional search capabilities and a range of other specialist policing functions during this period.
“Mutual aid officers are a vital part of the vast policing and security operation for these events.
“They will be provided with the necessary equipment and familiarisation training.
“They are coming to Northern Ireland to assist with the security operation and not every day policing of Northern Ireland. ”
PSNI Chief Constable Simon Byrne, who is currently in Washington, said it would be a “unique policing operation” for which the PSNI would require support.
“It is going to be a stretch and it is going to be a huge policing operation,” he told the BBC.
Mr Byrne added: “We are in close dialogue already with colleagues in England and Wales because we are likely to be asking for hundreds of specialist officers to come into Northern Ireland to support what will be a unique policing operation.
“We are really proud to play our part in 25 years of all the good news and optimism that fell out of the Belfast/Good Friday Agreement.
“If you think of the busy period across our summer months, we don’t normally ask for help from other parts of the UK.
“An operation like this, even if we are at full resource, we will have to rely on some specialist support.
“The scale of this means it will be a bigger ask than normal.
“My anticipation is that hundreds of officers from England and Wales will support what we are doing.”
He added: “We are a strong and resilient organisation and we have shown time and time again that we can step up to the challenge even in tough times.
“This is an operation which has been very carefully planned, we are getting advice and learning from recent events elsewhere in the UK and we want to do our part in making sure everybody can enjoy a celebration of the Agreement, and move around peacefully and without interruption.”
Mr Byrne has previously raised concerns about PSNI resources due to an ongoing funding shortfall. He said that would form part of his message during meetings in the US.
He said: “I come here with two messages. One is to investors that Northern Ireland is the safest part of the UK, but at the same time we need a police service that is sufficiently resourced to meet the challenges.
“We are not returning to the awful scenes of the past, the terrorist threat at the minute is about attacking the police service, it is not about deterring investors.”
Asked about the condition of senior detective John Caldwell, who was shot several times in an attack in Co Tyrone last month, Mr Byrne said: “John is receiving tip-top care but he remains seriously ill.”
