While for the month of December the exports-against-imports produced a $264million surplus, the deficit for the year to December grew from $2.85billion a year ago to $5.9billion.
ASB economist Nathan Penny said the trade data was in line with expectations, but the volatile petroleum and products component accounted for most of the increased deficit, having risen 19% during December.
''We suspect this jump in petroleum import values reflects the timing of shipments, as oil prices actually fell over during the month,'' Mr Penny said.
Annual imports for the year ended December reached a high of $63.4billion, up by $6.9billion, or 12%, from 2017.
StatisticsNZ international statistics manager Tehseen Islam said the lift in total imports in 2018 reflected large rises in the value of imported petrol and crude oil, as world prices had reached high levels in the second half of the year.
''In addition, recent falls in the New Zealand dollar has an upward effect on both export and import prices and their New Zealand-dollar values,'' he said.
The value of imported petroleum and products for the year to December was $7.7billion, up by $2.4billion, or 44%, from last year.
The value of annual exports for the year to December was $57.5billion, up by $3.9billion, or 7.2% from 2017.
Exports of meat and logs led the annual exports rise.
Meat exports increased $814million, or 12%, to $7.4billion, while logs, wood, and wood articles rose $596million, a 13% gain, to $5.2billion.
Sheep meat exports increased $546million, and beef was up $227million.
In the country's largest export commodity group, milk powder, butter, and cheese rose $356million, or 2.5%, to $14.3billion from a year ago.
Mr Penny noted the ongoing US-China trade friction posed a risk to his prediction New Zealand's trade deficit would reduce during the next 12 months.
''The outlook for global growth eased modestly over the second half of 2018 and the risk is that weaker growth translates into weaker export demand,'' he said.
