U.S. stock indexes slipped on Wednesday as investors awaited minutes from the Federal Reserve's meeting to gauge the health of the economy and the pace of interest rate hikes to stamp out spiking inflation.

After a brutal selloff in global equity markets in the first half of the year, nervous investors are keeping a close watch on central bank actions as they try to assess the impact of aggressive rate hikes on global growth.

With recent hawkish comments from Fed policymakers, most traders are factoring in another 75-basis-point increase later in July.

Trading on Wednesday was choppy, with focus on minutes from the Federal Open Market Committee's June policy meeting, where it raised policy rate by three-quarters of a percentage point. The minutes will be released at 2 p.m. ET (1800 GMT).

The Ukraine conflict, decades-high inflation and the Fed's pivot away from easy-money policy pushed the S&P 500 to its steepest first-half percentage drop since 1970. The benchmark index is down nearly 20% so far this year.

The U.S. 10-year Treasury yield hit a session high after falling earlier in the day to a five-week low. [US/]

A key part of the yield curve inverted for the first time in three weeks on Tuesday, reflecting growing angst in the world's biggest bond market over recession risks.

"It's a tug of war between people who believe the economy will remain strong enough and not go into recession, and those who believe we're already in one," Art Hogan, chief market strategist at B.Riley, said.

A survey from the Institute for Supply Management showed the U.S. services industry slowed less than expected in June, but a measure of services employment dropped to a two-year low, suggesting that demand for labor could be ebbing.

Another report showed U.S. job openings fell less than expected in May, pointing to a still tight labor market. The more comprehensive June nonfarm payrolls report will be released on Friday.

Oil prices have slipped in recent days as growing fears of demand destruction from a possible global recession outweighed supply concerns. The S&P 500 energy sector index fell 3.7%.

At 12:28 p.m. ET, the Dow Jones Industrial Average was down 158.97 points, or 0.51%, at 30,808.85, the S&P 500 was down 15.26 points, or 0.40%, at 3,816.13, and the Nasdaq Composite was down 35.12 points, or 0.31%, at 11,287.12.

Uber Technologies Inc and DoorDash Inc fell 4.1% and 7.7%, respectively, after Amazon.com Inc agreed to take a 2% stake in Just Eat Takeaway.com's struggling U.S. food delivery business Grubhub.

Rivian Automotive Inc gained 10.8% after the electric-vehicle maker's deliveries nearly quadrupled as it ramped up production.

Declining issues outnumbered advancers for a 2.27-to-1 ratio on the NYSE and a 1.70-to-1 ratio on the Nasdaq.

The S&P index recorded two new 52-week highs and 29 new lows, while the Nasdaq recorded 16 new highs and 77 new lows.