(For a live blog on the U.S. stock market, click or type LIVE/ in a news window.)
* Fed's rate-setting meeting under way
* Merck, P&G rise on quarterly profit beats
* Under Armour slides on N.America rev forecast cut
* U.S. consumer spending, prices rise moderately
* Futures off: Dow 0.39%, S&P 500 0.50%, Nasdaq 0.76% (Updates prices, adds comments)
By Shreyashi Sanyal
July 30 (Reuters) - Wall Street's main indexes were set to open lower on Tuesday, as worries about the scale of consensus at the Federal Reserve in favor of deeper cuts in interest rates ate into the positive sentiment that drove markets to record highs last week.
Initial price action pointed to losses of 0.4%-0.5% for the Dow Industrials and S&P 500, and a over a half percent fall for the Nasdaq, which included a dip in shares in Apple Inc ahead of its quarterly results later in the day.
Wall Street's main indexes have had a slow start to the week, retreating on Monday, and participants are bracing for what message the Fed will send if it pushes ahead with a well-telegraphed move to ease policy that has driven stocks higher since May.
With a quarter-percentage-point cut in rates fully priced-in, investors will watch for how Fed Chairman Jerome Powell manages debate about whether the stimulus is necessary and what that says about the attitude of the U.S. central bank to doing more in the months ahead.
"I think the Fed is going to leave the door open for further rate cuts even if they don't do 50 bps cut right now," said Scott Brown, chief economist at Raymond James in St. Petersburg, Florida.
Brown said concerns about trade policy and forward earnings growth are on the forefront.
As earnings season enters its third week, Apple's report after hours will provide a clear gauge on the impact of trade tensions with China on growth. Shares of the iPhone maker dipped 0.9% premarket.
Although trade talks between the world's two biggest economies resumed on Tuesday, expectations among traders for any breakthrough are limited.
Corporate earnings so far have been robust with nearly half of all S&P 500 companies that have posted second-quarter earnings, 76.1% have beaten bottom line estimates, according to Refinitiv data.
Goldman Sachs said on Monday it was lowering its earnings estimates for the benchmark index, citing weakness in economic activity and the outlook for margins, but said Wall Street is still set to extend its decade-long bull run into another year.
A report from the Commerce Department showed U.S. consumer spending and prices rose moderately in June, pointing to slower economic growth and benign inflation that could see the Fed cutting rates on Wednesday for the first time in a decade.
At 8:43 a.m. ET, Dow e-minis were down 107 points, or 0.39%. S&P 500 e-minis were down 15 points, or 0.5% and Nasdaq 100 e-minis were down 61 points, or 0.76%.
Shares in Merck & Co Inc rose 2.9% after the drugmaker reported quarterly profit above expectations.
Procter & Gamble Co gained 4.4% after the consumer goods maker beat estimates for quarterly revenue, boosted by price hikes and strong demand for its beauty products.
Pfizer Inc was set to fall for another day, last down 2.4%, after Morgan Stanley downgraded the drugmaker's stock to "equal-weight."
Under Armour Inc fell 11% after the sportswear maker cut its full-year revenue forecast for North America, its biggest market. (Reporting by Shreyashi Sanyal and Medha Singh in Bengaluru; editing by Patrick Graham and Arun Koyyur)