The UK and US are reportedly discussing the possibility of allowing pre-clearance checks at British airports for passengers taking transatlantic flights.
It would mean US Homeland Security staff conducting additional interrogations before a passenger is allowed to fly.
Similar procedures have been in place in Ireland for five years.
The initiative is being spearheaded by US homeland security secretary Jeh Johnson, the Telegraph reported.
He wants other countries to follow the example of Ireland, Canada and the Caribbean where passengers are “pre-cleared” before boarding an aircraft.
Officially, pre-clearance agreements are designed to ease congestion at US airports but critics argue it is a way of stopping unwanted people getting on a flight in the first place.
It effectively moves US immigration and passport control to the country of departure so passengers effectively arrive in America like domestic passengers.
A leaked German document claimed US authorities have approached five European countries over the possibility in July but only the UK has suggested it would be willing.
The document, seen by the Guardian, was a German government response to a parliamentary question and said that “Britain sees the advantages in allowing this procedure”.
It is understood the US has not made any formal request yet.
“Heathrow is an airport they have been looking at,” an industry source said.
Speaking to the Council of Foreign Relations earlier this week Johnson said adding other countries to the list was a policy goal.
“I regard it as a homeland security imperative to build more. To use a football metaphor, I’d much rather defend our end-zone from the 50-yard line than from our one-yard line.
“I want to take every opportunity we have to expand homeland security beyond our borders.”
A Home Office spokesman said: “Pre-clearance, which is already in operation in Ireland, is a means of speeding the entry of passengers through US airports.
“Pre-clearance checks are entirely separate from aviation security screening. The government has not received any request from a UK airport to introduce such measures.”