US President Donald Trump's steel tariffs have been delayed, so US allies can seek exemptions.

New Zealand has not been singled out for an exemption from US steel and aluminium tariffs - and that's gutting for the Government.

Trade Minister David Parker said he had not lost hope entirely but an exemption from the tariffs – which he once thought was a "50/50" possibility – was looking "less likely than it was".

US President Donald Trump has postponed introducing tariffs on steel and aluminium imports from some "allies", including the European Union, Canada and Mexico, for 30 days.

MARTIN MEISSNER/AP Steel plants like this one in Duisburg in Germany have earned a temporary reprieve from US tariffs, but New Zealand producers have not.

The US has also reached an agreement in principle with some other countries, including Australia, to avoid tariffs.

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But New Zealand, along with other countries such as South Africa and Japan, were not included in a list of countries that will be excluded for now from the tariffs.

"The omission of New Zealand from the list of exempted countries belies our positive bilateral relationship," Parker said.

"New Zealand is a strong security and defence partner for the US, and we enjoy a healthy and balanced trade relationship."

He noted that Japan, which reportedly described its omission as "extremely regrettable", was considering taking the matter to the World Trade Organisation.

TOM LEE/STUFF Trade Minister David Parker is disappointed.

"We are concerned at the possible implications for our domestic producers. While our exports of steel and aluminium to the US are not large, they are important to the businesses and workers in those industries," Parker said.

The situation with regard to the proposed tariffs remained unclear even in countries that were named as having an exemption, he added.

Parker said the Government was seeking clarity from the US administration on what would happen next.

He and Prime Minister Jacinda Ardern had written to their "US counterparts", and directed officials to engage at all levels, he said.

"I have also spoken to the US Ambassador to New Zealand," he said.