Major US indices were lower at the start of Thursday's trading, retreating from ground gained the session prior after the Federal Reserve signaled it wouldn't take more forceful steps against inflation.

The central bank's policy meeting had concluded Wednesday with a half-point rate increase as expected, but no sign that the Fed was willing to make a three-quarter point increase in the future, a reassuring sign to markets nervous about high borrowing costs.

Patrick O'Hare of Briefing.com said the prior session's rally -- in which indices gained around three percentage point by the close -- was fueled by "a counter-intuitive catalyst" and noted that high interest rates are traditionally not positive for equities.

"When the Fed is aiming to slow demand with rising interest rates, in an effort to squash inflation, it stands to reason that earnings growth is going to slow as well," he wrote in analysis.

"Market participants should be careful about what they wish for and rally around -- or at least be more discerning as they do because the Fed is still just getting started."

About 15 minutes into trading, the benchmark Dow Jones Industrial Average was down 1.1 percent at 33,671.81. The broad-based S&P 500 had lost 1.4 percent to 4,238.42, while the tech-rich Nasdaq Composite Index fell 2.1 percent to 12,695.38.

Twitter was trading 3.9 percent higher after Tesla boss Elon Musk disclosed he'd received more than $7 billion in equity committments to finance his takeover of the social media network.

Tesla was down 2.8 percent.