The proposal, which was reported by The Wall Street Journal in Monday editions, risks angering governments already irritated by U.S. demands that armed sky marshals travel on certain flights.
Under the plan, U.S. agents would work with local security officers at the airports, The Journal reports, reviewing passenger lists and questioning suspicious travelers who would likely be turned away once they reached the United States.
The airports targeted are: London's Heathrow and Gatwick airports, Narita near Tokyo, Charles de Gaulle in Paris, Frankfurt Main in Germany, Mexico City International and Schiphol airport in Amsterdam. Of the 70 million people who fly to the United States every year, those ports process 40 percent, the newspaper says.
U.S. Customs Service director Robert Bonner told The Journal that the program will be voluntary. It may begin with a pilot program at the airport in Warsaw, Poland to convince other countries to participate. Bonner told the newspaper the program could avoid flight cancellations and fines to airlines who carry travelers without proper documentation to the United States.
U.S. customs agents are already stationed outside the United States: They have operated in Canadian airports for some time. Under a more recent initiative, customs officers took up posts at foreign seaports to screen cargo headed to the United States.
But extending U.S. sovereignty to foreign airports raises both symbolic and practical questions: Could a U.S. agent arrest someone in Germany? Would a Homeland Security officer be allowed to carry, and use, a firearm in Japan? Who would have the final word on whether a person could fly to the United States? What would happen to those who were refused?
And, as one German official asked The Journal, would the United States reciprocate by allowing foreign officers to work in U.S. airports?
The Customs proposal comes amid tension between the United States and several foreign governments over recent security policies, particularly a U.S. proposal to use armed sky marshals on trans-Atlantic flights.
At a meeting last month, Britain and France were open to the idea of armed agents on flights, but other Europeans largely stuck to their reservations.
"We do not want weapons in the cabin," said Bo Eckerbert of the Swedish Aviation Administration. "It may even create more problems than it solves."
Airlines already have to supply U.S. authorities with more data on passengers on trans-Atlantic flights, but a December deal brokered between EU headquarters and Washington limited the use of such data to comply with EU privacy rules.
Finland's national carrier, Finnair, which flies to New York and other North American cities, is against the use of marshals, while package tour operator Thomas Cook, which operates charter flights between London and Orlando, Fla., also said it would not accept them.
Pilot organizations in Britain, Spain and other countries also expressed strong reservations.
Deputy Homeland Security Secretary Asa Hutchinson told reporters after the meeting that Washington would approach individual European nations to seek bilateral protocols on security measures for trans-Atlantic flights, including when and how air marshals would be used.
More than a dozen flights to the United States on British Airways, Aeromexico and Air France have been canceled or delayed since New Year's Eve because of security fears.
There are also concerns about a new system for tracking foreigners that was inaugurated in January.
Under the program, called US-VISIT foreigners entering U.S. airports and seaports from all but 27 nations will have their fingerprints scanned and their photographs taken.
The program will check an estimated 24 million foreigners each year, though some will be repeat visitors.
The only exceptions will be visitors from 27 countries — mostly European nations whose citizens are allowed to come to the United States for up to 90 days without visas.