a2 shares slump about 10% after the company says the US Food and Drug Administration has deferred a2's application to import infant milk formula products into the US

a2 Milk Company (ATM) shares have been clobbered on news that its application to import infant milk formula in the United States has been deferred.

The a2 shares slumped around 10% to just over the $5 mark after the company put out a brief statement just before the NZX began trading on Wednesday.

The company's managing director David Bortolussi said it had earlier in the day received notification from the US Food and Drug Administration (FDA) that, "at this time, the FDA is deferring further consideration of the Company’s request for enforcement discretion to import infant milk formula (IMF) products into the US".

"The Company has also subsequently been advised by the International Dairy Foods Association (IDFA) that equivalent letters have been sent to all pending enforcement discretion applicants, indicating that the FDA is deferring any further review at this time of all pending applications," Bortolussi said.

There was no indication given of when the application from a2 may be considered again.

The action on the NZX on Wednesday meant that a2 stock gave up virtually all the gains it made just over a week ago when there were media reports that the company was about to get approval - possibly within a week - from the FDA for its application.

On Tuesday, August 2 the company's stock briefly went into a trading halt after the price surged, before Bortolussi issued a statement at that time saying the company wishes to confirm that while we have been informed by the FDA that our application is under active review, "at this stage there is no certainty as to the outcome of the application or the timing of any approval".

Reuters reports that dairy companies in Australia and New Zealand have "queued up" to restock empty shelves in the United States with baby food, after the country recently relaxed its import policy to mitigate one of the biggest infant formula shortages in recent history.

It said that apart from Bubs Australia Ltd, UK-based Kendamil, Nestle SA and Danone SA, the FDA is yet to approve baby formula products from other applicants.