Researchers say it is relatively easy to clone the RFID (radio frequency identification) tags held in new US border passport cards and enhanced drivers' licences (EDLs).
A joint research paper from staff at the University of Washington and web security firm RSA shows how the RFID chips can be cloned from distances of up to 50 metres.
They also found that key anti-cloning techniques recommended by the US Department of Homeland Security (DHS) had not been used in the tags.
Since the beginning of 2008, Americans have been able to apply for the US Passport Card, which is also known as the Pass Card.
Containing a readable RFID chip, the card is intended to offer greater security and speed up border crossings for holders.
But the researchers have found that the RFID chips are cheap Class One Generation Two models. Any cost benefit obtained is countered by their vulnerability to cloning, says the report.
The chips are easier to clone because they do not use unique tag identifier codes, as recommended by the DHSbyt generic manufacturer's codes instead.