Apple Inc. (AAPL - Get Report) European supply chain tumbled Tuesday, pulling tech stocks in the region to the lowest level in more than a year, after chipmaker AMS AG (AMSSY)  forecast softer profit margins in the months ahead despite solid third quarter earnings. 

Swiss-listed AMS, which designs facial recognition sensors thought to be used in Apple's iPhones, including its new suite launched earlier this year, said third quarter earnings rose 13% to $60.2 million, on sale of around $480 million, which rose 57%, but expects a fourth quarter operating margin in the range of 16% to 20%. Analysts estimate that AMS earns about 40% of its revenues from Apple, although the company has consistently declined to identify its biggest customer.

"Ams is even more focused in its strategic approach as it pursues its growth strategy around the three pillars optical, image and audio sensing," the company said in a statement late Monday. "For the fourth quarter 2018, ams sees further sequential growth as it continues to ramp very high volume smartphone sensing products while its other end markets continue their positive contribution."

Ams shares were marked 29.7% lower in the opening hour of trading in Zurich and changing hands at Sfr35.00 each, the lowest since January 2017 and a move that extends its year-to-date decline past 60%.

Apple shares were marked 1.51% lower in pre-market trading and indicating an opening bell price of $217.32 each.

Stocks in Apple's European supply chain were pulled lower following the AMS results, which could portend weaker-than-expected demand for the tech giant's iPhones heading into the holiday season.

STMicroelectronics (STM - Get Report) was marked 5.8% lower in Amsterdam at €13.20 each while Dialog Semiconductor plc (DLGNF) , an Anglo-German chipmaker listed in Frankfurt whose power-management chip technology was recently licensed to Apple in a 600 million deal, fell 3.5% to €20.20 each. 

The Stoxx Europe 600 Technology subindex, the sector benchmark, slumped more than 3% in the opening hour of trading to 412.5 points, the lowest since August 2017.

Earlier this month, analysts at Goldman Sachs cautioned of "multiple signs of rapidly slowing consumer demand in China which we believe could easily affect Apple's demand there this fall", creating concern that the group's fourth quarter earnings, due on November 1, may indicate weakening iPhone demand amid a slowing global handset market. 

Goldman, which is holding to forecasts of 80 million in iPhone shipments over the three months ending in December, nonetheless cautioned that "should weak consumer demand persist and impact the higher end of the market Apple's potential to beat and raise in FQ4'18 earnings is likely reduced."