Apple shares have plunged in opening trade after the tech giant forecast its first quarterly revenue drop in 13 years.
Apple Inc shares have fallen 4 per cent after the company reported its slowest-ever rise in iPhone shipments, with an uptick likely only after the expected launch of iPhone 7 in September.
The March quarter is likely to be the weakest this year in terms of iPhone sales for the company, which forecast on Tuesday its first quarterly revenue drop in 13 years.
Shares fell to $US95.97 ($A136.86) at open on Wednesday, knocking off nearly $US20 billion from Apple's market value of about $US554 billion.
Tepid demand for the latest iPhones - that succeeded blockbuster sales of the iPhone 6 and 6 Plus - led Apple to sell 74.8 million iPhones in the first quarter. It expects to sell 50-52 million units in the March quarter.
But analysts said the depressed stock price could create a buying opportunity for long-term value seekers.
"We are looking for March to mark the trough in year-on-year iPhone unit growth, which should provide an attractive entry point into the stock ...," Goldman Sachs analysts wrote in a note.
At least 11 analysts cut their price targets on the stock.
Apple usually launches new iPhones in September and sells most devices in the December quarter. Unit sales typically drop over the next few quarters leading up to the next iPhone launch.
The iPhone 7 is expected to sport a new look with features such as waterproofing, wireless headphones and force touch as home button.
Up to Tuesday's close, Apple's stock had lost a quarter of its value since April 28, when it hit a record high of $US134.54.