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* U.S. service sector index at 2-year low -ISM survey

* Rivian gains as EV deliveries surge

* Indexes: Dow down 0.33%, S&P down 0.14%%, Nasdaq flat

July 6 (Reuters) - U.S. stock indexes endured topsy-turvy trading on Wednesday but were broadly flat heading into the Federal Reserve publishing the minutes from its latest meeting, as investors awaited new clues on the central bank's rate policy and inflation fight.

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 all three main benchmarks experiencing periods in both positive and negative territory. In the hour before the Fed minutes were due to be released at 2 p.m. EDT (1800 GMT), however, they held close to parity, with the Dow off marginally.

Investors are focused on the minutes from the Federal Open Market Committee's June meeting where it raised the policy rate by three-quarters of a percentage point.

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.

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 index fell 2.9%, leading decliners among the 11 subsectors.

By 1:30 p.m. EDT, the Dow Jones Industrial Average fell 103.08 points, or 0.33%, to 30,864.74, the S&P 500 lost 5.18 points, or 0.14%, to 3,826.21 and the Nasdaq Composite was flat at 11,321.69.

Uber Technologies Inc and DoorDash Inc fell 3.6% and 7.1%, 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 11.8% after the electric-vehicle maker's deliveries nearly quadrupled as it ramped up production. (Reporting by Amruta Khandekar and Bansari Mayur Kamdar in Bengaluru and David French in New York Editing by Shounak Dasgupta and Matthew Lewis)