It comes as the Ministry for the Environment considers new research showing how much money rules governing GM testing have cost the country.
Environment Minister Amy Adams has ruled out any changes to the GM regulations.
Gene scientist Dr Michael Dunbier said field trials on GM ryegrass in the United States were being done by Pastoral Genomics, an agricultural research body funded by the farming industry groups and the government.
The trials were on "cisgenic" - a form of genetic modification that uses genes from a single species.
Dr Dunbier, a director of AgResearch, said there were also plans to hold a field trial in Australia.
He said barriers included being able to produce enough seed in New Zealand in the laboratory for the Australian trial.
"Carrying out trials offshore does not decrease the need for trialling in New Zealand, but is an important part of the information likely to be needed for a New Zealand field trial application."
He said the overseas trials meant another step in the research process and added to the cost. It also delayed the chance to properly measure benefits to New Zealand with trials here.
"The key question New Zealand needs to evaluate is do the potential benefits of the technology outweigh any possible risks. Unfortunately, we cannot properly assess either without further research in the field in New Zealand."
Dr Dunbier said Pastoral Genomics had commissioned research on public attitudes to genetic modification. It included a response showing only 23 per cent of people believed New Zealand's "clean green" image would be adversely affected by the "cisgenic" grasses.
Sustainability Council director Simon Terry said references to "cisgenic" grasses were an effort to change the language about GM to reduce negative effects on public opinion.
Millions of dollars in government grants were being used as part of a research and PR strategy to get GM grasses on the market in New Zealand.
The public wanted openness on GM issues, he said, and the spin strategy detracted from that.
The Greens' spokesman on genetic modification, Steffan Browning, said the GM-related science community was strident in its approach.
"This is part of a co-ordinated response in pushing genetic engineering in New Zealand."