New Zealand shares fell on Wednesday as Asian stocks were mixed after US President Donald Trump threatened a 50% tariff on copper and flagged upcoming tariffs on semiconductors and pharmaceuticals.

The S&P/NZX 50 Index fell 0.70% or 90.41 points to close at 12,768.61.

Trump on Tuesday said he would impose a 50% tariff on imported copper and soon introduce tariff impositions on semiconductors and pharmaceuticals, Reuters reported on Tuesday.

"The delay in the imposition of new tariffs on some of the U.S.'s major trading partners to August 1 has simultaneously kicked the proverbial can down the road and supported the notion that the loftier tariff rates are a negotiating ploy," said Kyle Rodda, senior financial markets analyst at Capital.com, as quoted by Reuters.

In domestic news, the monetary policy committee of the Reserve Bank of New Zealand decided to hold the official cash rate (OCR) steady at 3.25%, citing easing domestic inflation pressures and significant spare capacity in the economy, while signaling potential rate cuts later this year if inflation trends as expected, according to a statement.

Meanwhile, a total of 1,828 metric tonnes (MT) of products were sold during the Global Dairy Trade (GDT) Pulse auction held Tuesday, within the supply range of 1,700 MT to 2,000 MT, according to data from the trading platform.

Also, New Zealand residential construction costs rose 0.6% in the June quarter, largely due to the absence of last year's 1.1% drop rather than renewed price pressures, according to the Cordell Construction Cost Index, compiled by property data company Cotality, formerly known as CoreLogic, according to multiple media reports.

In corporate news, Infratil (ASX:IFT) said the changes under the US's One Big Beautiful Bill Act are materially better for its portfolio company Longroad than expected before, according to a Wednesday Australian bourse filing.