When compared to the estimates provided by Apple to its investors in November, the revenue amount took a drastic nosedive, while the "other income/(expense)" category went through the roof, reaching approximately $550 million from an initial estimate of $300 million.
Cook said other factors will also pull down Apple's revenue, including the timing of its iPhone launches previous year and a strong dollar that means lower revenues when converted to United States currency.
"Lower than anticipated iPhone revenue, primarily in Greater China, accounts for all of our revenue shortfalls to our guidance and much more than our entire year-over-year revenue decline".
Under the new guidance, Apple says revenue will be around $84bn, well short of the $89-93bn range Apple had estimated and a sizeable drop from the $88.3bn revenue haul Apple reported in Q1 FY 2018.
Cook said that while Apple anticipated some challenges in key emerging markets in the first quarter ended Dec 29, 2018, it did not foresee the magnitude of the economic deceleration, particularly in China.
But the biggest problems came from lackluster sales in China and equally disappointing iPhone upgrades. "Apple innovates like no other company on Earth, and we are not taking our foot off the gas", he explained. He said the company was performing strongly outside of the communist nation. China's economy has been pinched by the ongoing Sino-US trade war which is spilling over to other Asian economies. Wearables grew by nearly 50 percent year-over-year, thanks to holiday sales of the Apple Watch and AirPods. "The already shaky foundation for Apple owing to the likelihood of the company's products being enlisted into the tariffs scuffle saw their latest move to lower revenue outlook packing a punch for share prices".
The company now expects revenue of around $84 billion (£67bn) for the October to December period, well below previous predictions of up to $91bn (£72bn).
Apple's shares were halted after the stock market closed Wednesday.
Apple's surprise announcement added to concerns about the ability of U.S. companies, particularly its technology giants, to navigate an increasingly uncertain economy and a continuing trade war between the United States and China. In an unscheduled update it said there had been a "significantly greater impact than we had projected" from slower growth in emerging markets. Firstly, it was the timing of the iPhone XS and XS Max release where both had gone on sale earlier compared to the iPhone X. He also cited the strengthening of the U.S. dollar versus other currencies as well as supply constraints which affected sales of its latest Apple Watch, iPad Pro and MacBook Air.
Apple was down as much as almost 10% on the news.