Apple's core assembly partner, Foxconn, saw net profits drop 12.6 percent in the fourth quarter, a figure almost certainly linked to declining iPhone sales.

Profits were approximately $2 billion, versus about $2.3 billion in the same quarter a year ago, according to the Wall Street Journal. That's despite revenue rising 4.6 percent to $58.69 billion. The consensus estimate for profits sat at $1.2 billion prior to the announcement.

Foxconn didn't elaborate on the results, but the manufacturer is known to depend on Apple for as much as half of its revenue, and the iPhone is by far the most critical product to Apple's bottom line.

On Jan. 2 Apple warned investors that its December-quarter revenue would come closer to $84 billion, missing original guidance by at least $5 billion. The company ultimately reported $84.3 billion in revenue, down from $88.3 billion a year prior.

The miss was blamed squarely on iPhone sales, which fell 15 percent year-over-year to $52 billion. Narrowing further, Apple said it faced the harshest situation in China, hampered by factors like exchange rates, general economic woes, and tough competition from lower-priced local alternatives.

Thanks to improved prices and trade-in offers Chinese demand has been recovering. It's doubtful however that sales will resume real growth until the fall, when 2019 iPhone designs ship.