When the AI computing race extends from chips to every corner of global capital markets, a wave of bond issuance led by American tech titans is triggering heightened alarm at the highest levels of the European Central Bank. On September 1, the ECB published a rare blog post delivering a stark warning about the "major incursion" of US hyperscalers into the eurozone bond market: if this trend persists, it could push up financing costs across all industries and potentially create spillover effects on eurozone sovereign bond markets.

The AI "cash burn" is accelerating: hyperscalers may need to borrow over $1 trillion by 2028. The ECB noted in its blog that AI infrastructure demands massive investment—the enormous data centers and the electricity needed to power them have forced five US hyperscalers—Alphabet, Amazon, Meta, Microsoft, and Oracle—to shift from "internal self-funding" to "external financing." Credit analysts estimate that by 2028, the total AI-related capital expenditure needs of these five companies will exceed $1 trillion—equivalent to 3% of current US annual GDP. This scale has far surpassed what internal corporate cash flows can cover, pushing them toward global bond markets.

The "crowding-out effect" in euro bond markets is becoming visible: the €40 billion outstanding amount already accounts for nearly 10% of new issuance. ECB data shows that the presence of US hyperscalers in the eurozone bond market is rising sharply: in the first half of 2026, Alphabet and Amazon alone issued 25 tranches of bonds in the euro and Swiss franc markets, with total outstanding amounts of approximately €17.5 billion and CHF 6.26 billion. In March this year, Amazon issued bonds worth up to €10 billion in the European market, split into eight tranches with maturities ranging from 2 years to 38 years. Although the €40 billion outstanding amount still represents a "relatively small share" of the overall market, the nearly 10% share of new issuance means the marginal impact is expanding rapidly. The ECB specifically pointed out that Amazon and Alphabet have become the largest issuers in the eurozone non-financial corporate bond market this year. Between 2025 and 2026, their share of "Reverse Yankee Bonds" issued in the eurozone nearly doubled. European pension funds and insurance companies are heavily buying hyperscaler bonds—by March 2026, such bonds accounted for 15% of the growth in euro corporate bond holdings. The automatic rebalancing by passive investors tracking bond benchmarks could further amplify the crowding-out effect.

Macro resonance: surging US Treasury yields and pressure on global bond markets. The ECB's warning coincides with a new wave of selling in global bond markets. On September 2, the US 10-year Treasury yield climbed to 4.816%, the highest level since late 2023; Japan's 10-year government bond yield broke above 3% for the first time since 1996; and Germany's 10-year yield rose to 3.377%, a record high since 2011. Against this macro backdrop, the massive bond issuance by US tech giants could further intensify market pressure. The ECB blog noted that new issuance volumes could test investor appetite, and expectations of even larger bond supplies could amplify this effect. ECB economists warned that tech giants' debt could effectively "saturate" the eurozone bond market, forcing issuers to offer higher yields to attract investors.

Threefold risks: from the "crowding-out effect" to credit ratings being "too optimistic." First, a broad increase in financing costs. The blog authors explicitly stated: "Large US tech companies, as their debt accumulates and their share in the bond market grows, could push up borrowing costs across all industries and potentially spill over to sovereign and supranational bond markets." ECB economists specifically warned that this trend could crowd out demand for European government bonds—while eurozone sovereign bond yields are already at 15-year highs. Passive investors tracking bond benchmarks will automatically increase their holdings in the tech sector, exerting additional pressure on competing bonds. Eurozone sovereign bond yields hit multi-decade highs on Monday, with Germany's 10-year yield rising to 3.32%, the highest since 2011. Second, investors' "absorption capacity" faces a test. New issuance volumes could "test investor appetite," and expectations of larger bond supplies could amplify this effect, further pushing up borrowing costs across the entire market. Third, credit ratings may be "too optimistic." The blog authors raised a sharper question: rating agencies' assessment of the sector "may be based on assumptions about future revenue growth and leverage ratios that may not withstand the test of time, thereby exacerbating the risk of mispricing credit risk."

The "Sword of Damocles" over sovereign bond markets. Although the ECB acknowledged that "no obvious spillover effects have yet emerged in the eurozone" because tech bond issuance remains relatively small to date and European sovereign bond markets are "resilient," the blog also warned that the battle for AI supremacy means the impact of such debt issuance "is likely to intensify in the coming years." Reports have further indicated that the massive financing needs of AI data centers are increasingly driving major US tech companies to issue euro-denominated debt—a practice that risks crowding out investor demand for European government bonds. As hyperscalers' weight in bond indices continues to grow, investors' asset allocation could be "mechanically rebalanced" from sovereign bonds toward tech bonds. The ECB warned that this "could be just the beginning of an unprecedented financing wave that will significantly reshape bond markets, including the eurozone, prompting issuers, intermediaries, and investors to adapt." Although the blog emphasized that no "obvious spillover effects" have appeared in the eurozone so far, the intense competition for AI dominance means these effects are likely to increase in the coming years. The ECB raised a key market functioning question: can eurozone financial markets smoothly absorb such a large-scale and concentrated debt inflow?

US tech giants have already issued approximately $200 billion in bonds so far in 2026. Hyperscalers' bond issuance this year has reached $220 billion, more than double the full-year total for 2025. Morgan Stanley expects global AI-related bond issuance to approach $570 billion in 2026. The blog authors concluded with a telling judgment: "This could be just the beginning of an unprecedented financing wave that will significantly reshape bond markets, including the eurozone, prompting issuers, intermediaries, and investors to adjust."