New Zealand librarians are worried about the impact of possible changes to copyright law as a result of the Trans Pacific Partnership agreement that is being negotiated.
They believe the costs of buying books would increase greatly if a ban on parallel importing was reintroduced.
And they believe an extension to the duration of copyright beyond the present 50 years after the death of an author to 70 years could affect library digitisation programmes.
The 13th round of talks for the free trade deal is finishing up in San Diego.
The negotiations are secret but it is known that the United States entertainment industry is pushing for stronger copyright provisions among the 11 countries in the Asia-Pacific region negotiating the deal.
The Library and Information Association of New Zealand Aotearoa (LIANZA), representing 450 New Zealand libraries, has joined with sister library organisations in other TPP countries and an international umbrella group to voice their concerns.
Tony Millet of Auckland, a former librarian at Waikato University and a LIANZA copyright specialist, said if the US succeeded in getting a ban on parallel importation written back into New Zealand laws, it would force up the cost for libraries of buying books.
It would also slow down the speed at which books were supplied to libraries.
Parallel importing, which was legalised in 1998, is when a lawfully made product is imported but not through the producer's local representative.
On the issue of extending the duration of copyright, Mr Millet said it would not benefit authors because the copyright extended beyond death.
It would add restrictions to what libraries were able to digitise now and affect end-users because they would not have access to them.
In the United States, the duration of copyright is 70 years for creative and artistic works produced after 1978.
Australia used to have a 50-year duration like New Zealand but changed it to 70 years in 2006 as part of its bilateral free trade agreement with the United States.
Mr Millet said there was also a concern that there could be an increase in the protection given to technological protection measures (TPMs) on material such as videos and DVDs (such as the zone restrictions on DVDs) which would prevent libraries overriding TPMs for their users.
This has been permitted in New Zealand since 2008.