THE US Consulate-General would like to clarify US policy with regard to the ''cross-linking service'' described in your story headlined, ''Old visas validated'' (South China Morning Post, May 6).
The article explains that an endorsement in a new BN(O) passport will ''cross link'' a visa from an old BDTC passport. In the case of the United States, a traveller wanting to use a visa remaining valid in an old passport must present to the immigration inspector at the port of entry both the old passport intact with the visa in it and the new passport. An endorsement in the new passport or the visa detached from the old passport will not suffice.
For this reason, we recommend that holders of new passports apply for new visas. Applications with valid visas who wish to transfer them to new passports can be accommodated through the US Consulate General's ''drop box'' service. The ''drop box'' service is provided for the convenience of tourist and business travellers.
Qualified applicants aged 55 or older, applicants who have previously had a US visa of one-year validity or longer and who have been to the US and returned, and persons wishing to transfer a valid US visa to a new travel document may use the ''drop box''service. It is available from 8.30 to 11.30 am and from 1.30 to 3.30 pm Monday through Friday. Visaed passports can be picked up at 4 pm the following working day.
VALLERIE STEENSON Information Officer US Consulate General