The Secret Service also have diplomatic immunity which will allow them to shoot to kill a would-be assassin without fear of prosecution.
As part of the “evacuation route” plan, they would be able to spirit the President by chopper to one of the carriers where a jet is on standby to take him back to the United States.
A source said: “It sounds like James Bond stuff but the Americans treat the personal protection of their President with the utmost seriousness.
“They have plans in place for all possible incidents, despite how unlikely they might seem or how much security is already in place.
“They have moved the aircraft carriers in place as a precautionary measure as part of those plans.” The warships are no stranger to Irish shores — a US aircraft carrier was filmed at Culdaff Beach in Inishowen, Co Donegal just last Christmas, with the footage posted on YouTube.
President Obama will be staying at the Lough Erne Resort in Enniskillen in a suite for the G8. His wife Michelle and their daughters Malia and Sasha will accompany him to Belfast’s Waterfront Hall on Monday morning before they travel to Dublin.
It isn’t yet known if the family will do a short walkabout and greet the public in Belfast tomorrow.
While in Dublin, with Secret Service agents guarding the family, the US First Lady will visit Trinity College where she will explore archives documenting the Obamas' Irish ancestry.
Mrs Obama will also view the world famous Book of Kells.
Later that day, she will meet with the staff and families of Embassy Dublin and join young people for a special performance by the Riverdance company at the historic Gaiety Theatre.
On Tuesday, the First Lady will visit the picturesque Wicklow Mountains National Park. The Obamas will then travel to Germany on Wednesday.
The Secret Service was directed to protect the President of the United States after the assassination of President William McKinley in 1901.
On their website they state: “The Secret Service is world-renowned for the physical protection it provides to the nation's highest elected leaders and other government officials.
“In general, permanent protectees, such as the president and first lady, have details of special agents permanently assigned to them. The protection of an individual is comprehensive and goes well beyond surrounding the individual with well-armed agents.”
As part of their meticulous planning ahead of G8 the Secret Service even bought tractors so that agents can pose as farmers in the Fermanagh countryside.