Why Did U.S. Equities and Tesouro Direto Fall on Monday?
The U.S. government's rejection of an Iranian peace proposal sent oil prices surging nearly 4% toward $108 a barrel, reviving global inflation fears and pushing government bond yields in the U.S. and Brazil to new highs. The move hit global stock markets hard on Monday (09/28/2026): the S&P 500 declined 0.59% to close at 7,698.04 points, while long-term Treasury yields reached peaks not seen in nearly two decades.
The spillover hit Brazilian fixed income almost in real time. With the international backdrop pointing to high interest rates for longer in the United States, Tesouro Direto fixed-rate bonds traded back near the 14% per year mark, while IPCA-linked inflation bonds registered mark-to-market losses on the day.
How Did the Geopolitical Stalemate Push Oil to $108?
The direct trigger for market stress was the announcement that U.S. President Donald Trump had rejected a temporary peace proposal presented by Iran at the United Nations General Assembly. According to international media reports and Reuters, the Iranian plan called for reopening the Strait of Hormuz within seven days in exchange for immediate sanctions relief and the unfreezing of Tehran's assets.
Washington's refusal confirmed to the market that tensions in the Persian Gulf will continue to constrain energy supply in the near term. As a result, Brent crude futures rose 3.75% to $108.23 a barrel, while WTI advanced 2.85% to trade at $95.97.
According to StoneX market intelligence analyst Bruno Cordeiro, Washington's stance dashed initial expectations that export flows from the region could be quickly restored. Without the prospect of supply normalization, the commodity remains firmly entrenched as the primary driver of global inflationary pressure right now.
Why Did Long-Term U.S. Interest Rates Hit Decades-Highs?
The surge in oil triggers a chain reaction in the U.S. economy: more expensive commodities drive up shipping and production costs, which reignites inflation and forces the Federal Reserve (Fed) to keep interest rates high. According to market analysts interviewed by Reuters, the energy sector has been the sole persistent source of upward pressure on American prices, serving as justification for an openly restrictive monetary stance.
Given this picture, investors scrambled to recalculate the trajectory of the U.S. benchmark rate. The market began pricing in a 68% probability that the Fed will implement another interest rate hike at its upcoming meetings.
Impact on U.S. securities: The 10-year Treasury yield hit its highest level since June 2007 during the session. Meanwhile, the 30-year bond continues to fluctuate at levels not seen since 2004. When risk-free instruments pay such high returns, corporate capital costs soar, and the equity risk premium for holding S&P 500 stocks becomes unfavorable.
Additionally, minutes from the Bank of Japan's (BoJ) recent meeting released on Monday reinforced that Japanese monetary officials see room to continue raising interest rates as the country's core inflation approaches the 2% target. Simultaneous tightening across the world's largest economies reduces global liquidity and compresses equity market multiples.
What Changed in Brazilian Tesouro Direto Yields?
The shock to U.S. yields and oil immediately spilled over into Brazilian yield curves. Throughout Monday's opening and trading sessions on Tesouro Direto, public bond rates surged, led by fixed-rate maturities.
| Bond | Previous Close | Current Rate (09/28) | Change |
|---|---|---|---|
| Tesouro Prefixado 2029 | 13.85% | 13.93% | +8 bps |
| Tesouro Prefixado 2032 | 14.08% | 14.15% | +7 bps |
| Tesouro IPCA+ w/ Coupons 2037 | 7.49% | 7.55% | +6 bps |
| Tesouro Prefixado w/ Coupons 2037 | 14.06% | 14.12% | +6 bps |
As Tesouro Direto pricing data shows, longer fixed-rate bonds climbed back above the symbolic 14% per year threshold. For investors holding these bonds in their portfolios until maturity, the move translates to a temporary drop in balance sheet value due to mark-to-market accounting, as higher yields reduce the present value of the bond.
Why Did Nvidia Gain 3.2% Amid the Broad Sell-Off?
While the broader market and consumer discretionary sector led losses in New York, Nvidia stood out as a major isolated exception of the day in the S&P 500. Shares of the semiconductor giant jumped 3.2% in the same trading session.
The divergence from the general trend followed the company's announcement of a $150 billion share buyback program. It marks the largest share repurchase authorization in company history, insulating the stock from the liquidation wave that hit the rest of the technology sector and the broader U.S. stock market.
What to Monitor Going Forward
For anyone investing in the Brazilian market or holding international assets in their portfolio, Monday's events serve as an important reminder of the transmission channel between geopolitics, commodities, and fixed income.
The central points to keep on your radar include:
- Oil trends in the Middle East: Brent remaining near or above $108 will keep global central banks on high alert, precluding interest rate cuts.
- U.S. stock multiples (S&P 500): With Treasuries offering long-term returns at historically high levels, equity risk premiums remain compressed. This environment favors a cautious stance on international equities with stretched valuations.
- Opportunities and volatility in Fixed Income: Rising fixed-rate yields approaching 14% attract investors focused on holding bonds to maturity. However, those seeking short-term mark-to-market gains should expect continued high volatility until the external environment settles.
