US STOCKS-Wall St set to open lower as U.S.-China trade optimism fades

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* Sept. PMI reading set to kick off data-heavy week

* Apple gains on tariff exemptions

* Wall Street posts worst session in 2 weeks on Friday

* Futures: Dow down 0.19%, S&P off 0.08%, Nasdaq flat

(Adds comment, details; updates prices)

By Medha Singh and Ambar Warrick

Sept 23 (Reuters) - U.S. stock indexes were set to open slightly lower on Monday as investors were cautious about progress in Sino-U.S. trade talks and waited for a slew of economic reports to gauge the health of the domestic economy.

The indexes recorded their worst session in about two weeks on Friday - ending a three-week run of gains - after a Chinese agriculture delegation canceled a visit to Montana. U.S. and Chinese officials described the deputy-level trade talks last week, meant to lay the groundwork for high-level negotiations in October, as being "constructive" and "productive". chances of a complete deal are pretty remote, people are pinning their hopes on any deal where they just stop the escalation (of the trade war)," said Scott Brown, chief economist at Raymond (NS: RYMD ) James in St. Petersburg, Florida.

After the U.S. central bank's fairly upbeat assessment of the domestic economy, investors will monitor a host of economic data in the final week of the third quarter, including core personal consumption data - the Fed's preferred inflation measure - and final growth figures for the second quarter.

Data from the IHS Markit Purchasing Manager's Index (PMI) is expected to show U.S. manufacturing activity holding steady at 50.3 in September, and services PMI as rising to 51.5 from 50.7 in August.

The report, due at 9:45 a.m. (1345 GMT) ET, follows disappointing business surveys from across the euro zone. did see an increase in factory output and industrial production number reported last week, but the trend is clearly lower and that's a bit of a concern," Raymond James' Brown added.

Investors will also be watching for a speech by Federal Reserve Bank of New York President John Williams (NYSE: WMB ) at the 2019 U.S. Treasury Market Conference.

At 8:52 a.m. ET, Dow e-minis 1YMcv1 were down 51 points, or 0.19%. S&P 500 e-minis EScv1 were down 2.25 points, or 0.08% and Nasdaq 100 e-minis NQcv1 remained unchanged.

Apple Inc AAPL.O , the second most valuable stock on the Nasdaq, rose 0.2% in premarket trading after U.S. trade regulators approved 10 out of 15 requests for tariff exemptions by the iPhone maker. supplier Micron MU.O , which makes computer memory drives, was marginally higher.

Boeing (NYSE: BA ) .BA.N dropped 0.7% after a Reuters report that European antitrust regulators were set to investigate the plane maker's $4.75 billion bid for the commercial aircraft arm of Brazil-based Embraer SA EMBR3.SA . the chief of the U.S. Federal Aviation Administration is set to detail progress on the Boeing 737 MAX aircraft to international air regulators, who are divided about returning the grounded jet to flight after two fatal crashes. Networks Inc JNPR.N rose 2.3% as Needham upgraded the network gear maker's stock to "buy".