British fliers may have to fork out more money for flights to help fund US immigration officers stationed in UK airports, an industry source said.
Discussions between the UK and United States on the potential deployment of US Customs and Border Protection officers to the country are ongoing.
The system, in place at airports in six countries including the Irish capital Dublin, allows passengers flying into the US to avoid long queues at US immigration and customs when they touch down on American soil.
It would involve law enforcement officers checking travel documents, passports, visas and making sure travellers abide by strict customs and agriculture importation rules at UK airports before flights are boarded.
The industry insider said the US was very keen for pre-clearing and it was unlikely that the question of whether officers were armed or not, as is the case in America, would be a deal-breaker.
The industry insider said: "They are much more concerned about having pre-clearing granted than they are about having their officers walking around like in the US.
"The real challenge is who's going to pay.
"The US wants airports to pay for it; airports will say 'that's fine' but then increase charges to airlines.
"I would imagine airlines would pass on some of that additional cost to flight users," he added.
He said if airlines were not prepared to foot the bill then the plan may not happen.
The US government would need to negotiate with individual airports as they would have to adapt their operations, but the plan would also require approval by the UK Government.
One change could mean introducing a separate, sealed-off part of airport terminals for US security checks.
Manchester and Edinburgh airports are understood to be discussing the programme separately.
A spokesperson for the Airport Operators Association said: "Airports are always looking for ways to improve the service we offer passengers and pre-clearing US immigration in the UK is one such possibility.
"However, there are a number of practical considerations on both the UK and US side that need further work to make it a reality."
The US has special immigration checks in six countries around the world, with more than 600 law enforcement officers are stationed at 15 locations.
Pre-clearance operations in Dublin and Shannon in Ireland opened in 2008 and last year officers processed about 1.18 million people in Dublin and 204,000 people in Shannon.
In total, 18 million people went through the pre-clearance system around the world last year - 15% of all commercial air travellers flying into the US.