Signatories to the UN's Cartagena Protocol on Biosafety, which came into force in September last year, decided at a conference here on a "rigorous system" for handling, transporting, packaging and identifying genetically-engineered exports.
The agreement "foiled attempts by the USA and other GM exporting countries to weaken this newborn international agreement on GMOs (genetically modified organisms)", the Friends of the Earth environmental group said in a statement.
The US was quick to express its disappointment. "We understand the concerns that countries have to protect their biodiversity, but we believe you can't just erect walls and have regulatory procedures that are not based on science," biotech trade policy spokeswoman Deborah Malac said.
"Our biggest disappointment is that we feel they are moving down a path away from practical steps. They are moving very, very quickly in a direction without being sure parties can implement their obligations."
The US has not signed the protocol, which has been ratified by 86 countries and the European Union (EU), and lobbied hard on the sidelines of the conference for the minimal labelling of GM products, claiming they posed no threat to human health or to the environment.
Critics, however, have dubbed such products -- known as GMOs or living modified organisms (LMOs) -- "Frankenfoods", after the fictional man-made monster Frankenstein.
The US is the world's biggest producer of GM crops and is already involved in a battle over export regulations in the World Trade Organisation (WTO), where the EU wants strict labelling requirements.
Genetic modification can involve the introduction of genes from one plant to another or the switching of genes between plants and animals to change the way they develop, usually to protect them from disease or enhance their commercial value.
Under the new system, all shipments of GMOs such as seeds and fish that are meant to be introduced directly into the environment must be clearly identified as "destined for contained use", the United Nations Environment Programme (UNEP) said in a statement.
The common, scientific and commercial names of the modified organisms along with the "transformation event code" must be documented, as well as the contact details of the traders, while any handling and storage requirements are to be clearly indicated.
Documentation must also provide contact details in case of an emergency, identify the GMO's risk class and specify how the GMO is to be used.
All bulk shipments of genetically-engineered crops intended for food, animal feed or processing, such as soybeans and maize, are to be labelled "may contain LMOs", the UNEP said.
"Now that a system for identifying and labelling GMO exports has become operational, countries can enjoy the benefits of biotechnology with greater confidence while avoiding the potential risks," said Hamdallah Zedan, the Protocol's executive secretary.
"This rigorous system for handling, transporting, packaging and identifying GMOs is in the best interests of everyone - developed and developing countries, consumers and industry, and all those who care deeply about our natural environment," he said.
The conference also set up a group of legal and technical experts to develop regulations by 2008 covering liability and redress for damages resulting from transboundary movements of GMOs.
The protocol forms part of the Convention on Biological Diversity, adopted by 150 countries after the Rio Earth summit in 1992, which aims to protect all forms of life from the ravages of human development.