Prime Minister John Key says good progress is being made towards a Free Trade Agreement (FTA) with South Korea.
Mr Key is in Seoul for a two-day Nuclear Security Summit beginning on Monday.
On Sunday, he met with South Korean President Lee Myung-bak to discuss progress over a potential bilateral trade deal.
He told Radio New Zealand's Morning Report programme on Monday that South Korean farmers are putting up much resistance to free trade deals, but good headway is being made.
"There's definitely a willingness on the Korean side to complete a deal. There's a lot of interest, obviously, on our side. Korea's our fifth largest market; two-way trade's pretty evenly balanced - it's about $3 billion.
"The worrying thing up here is that, without an FTA, companies like (kiwfruit marketer) Zespri and (dairy cooperative) Fonterra could effectively be locked out of this market."
Mr Key says tariffs paid by New Zealand exporters are high and the lack of an FTA is a huge competitive disadvantage.
The Prime Minister also hopes to discuss progress towards a trans-Pacific trade deal with United States president Barack Obama at the summit.
John Key says New Zealand can proudly stand on its record of being nuclear-free.
Mr Key says the summit it is about trying to reduce and eventually eliminate the threat of nuclear terrorism and New Zealand can contribute in a meaningful way and demonstrate it is showing leadership in this area.