Apple Inc. (AAPL  )'s ambitious endeavor to develop its own cellular modem for iPhones, aiming to replace Qualcomm Inc. (QCOM  ) as its primary supplier, has encountered notable challenges.

This complex undertaking has reportedly led to a delay in Apple's plans, pushing back the introduction of its custom cellular modem to late 2025 or early 2026.

What Happened: As reported by Bloomberg, individuals close to the matter reveal the intricacies involved in substituting such a crucial component have proven more daunting than anticipated.

The custom modem, a key element enabling phones to connect to cellular networks for calls and internet access, is a cornerstone of Apple's strategy to enhance technological self-reliance.

Why It Matters: Despite the concerted efforts of thousands of Apple employees since 2018, the company is still grappling with the complexities of this project.

The objective is not only to match but to surpass the data download speeds offered by current technologies. Sources privy to the project's progress, who preferred anonymity, expressed skepticism to Bloomberg about achieving this goal given the state of development.

Qualcomm's stock was flat around the close. Meanwhile, Apple's stock saw a modest increase, trading less than 1% higher at $189.45.