The US Federal Reserve held its policy rate steady at 3.50%-3.75% at its latest meeting, but the decision was not unanimous. Three officials voted for a 25-basis-point rate hike, according to the Fed statement.

Fed Chair Kevin Warsh reiterated the central bank's commitment to the 2% inflation target and said he sees no softening of that goal. He noted that both nominal and real interest rates have risen across the entire Treasury yield curve since the last meeting, but avoided giving forward guidance on future policy.

The 30-year yield reached 5.2369%, its highest level since July 2007, when it hit 5.2387%. The 10-year yield also rose, gaining 8 basis points to 4.69% and later trading at 4.70%.

The yield spread between 2-year and 30-year Treasuries widened as long-term yields outpaced short-term yields. Analysts interpret the rise in long-term bond yields as a sign investors worry the Fed may not be aggressive enough in controlling inflation.

Waterer said the rise in the 30-year yield reflects market expectations that inflation will remain elevated longer than the Fed currently projects. He partly attributed the rise to climbing oil prices since the start of the US-Iran conflict, which add to inflationary pressures. Waterer added that the Fed is taking a phased approach to rate hikes, but the bond market is pricing in the eventual need for more aggressive tightening due to sustained oil price rises.

The rise in US long-term bond yields is increasing global borrowing costs, supporting the US dollar, and putting pressure on growth stocks and emerging market assets. Analysts warn that if the 30-year yield continues to rise, it could become a negative factor for global stock markets and increase foreign exchange volatility.