(For a Reuters live blog on U.S., UK and European stock

markets, click LIVE/ or type LIVE/ in a news window)

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Nvidia ( NVDA ) edges lower ahead of annual software developer

conference

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Tesla slips after RBC lowers price target

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Alphabet falls on $32 billion deal to buy Wiz

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Indexes down: Dow 0.79%, S&P 500 1.20%, Nasdaq 1.77%

(Updates to mid-session trading)

By Pranav Kashyap and Johann M Cherian

March 18 (Reuters) - Wall Street's main indexes were

lower on Tuesday on worries about the economic impact of U.S.

tariff policies ahead of a monetary policy decision from the

Federal Reserve.

The Fed's two-day rate-setting meeting kicks off on Tuesday,

and expectations are that the central bank will keep interest

rates steady, according to data compiled by LSEG.

Several U.S. central bank officials have cautioned against

hasty moves and said they would wait for data to see the impact

of tariffs before making any policy shifts.

"I don't think they (Fed) know exactly how this (trade

policy) is going to play out," said Brent Schutte, chief

investment officer at Northwestern Mutual Wealth Management

Company.

Markets were taking a pause after all three major indexes

gained more than 2% each over the past two sessions as investors

capitalized on discounted U.S. equities following last week's

selloff.

The S&P 500 had tumbled more than 10% from its

February peak, signaling the benchmark index entered a

correction phase.

The blue-chip Dow is trading close to correction levels,

while the tech-heavy Nasdaq confirmed it is in a correction on

March 6.

Trump and Russian President Vladimir Putin discussed moves

to end the Ukraine war on Tuesday and the White House said their

phone call was going well.

At 11:47 a.m. ET the Dow Jones Industrial Average

fell 330.66 points, or 0.79%, to 41,510.97, the S&P 500

lost 68.07 points, or 1.20%, to 5,606.90, and the Nasdaq

Composite lost 314.19 points, or 1.77%, to 17,494.16.

Communication services led sectoral declines on

the S&P 500 with a 2.7% drop.

Alphabet fell 3% after the company said it would

buy Wiz for about $32 billion in its biggest deal as the Google

parent doubles down on cybersecurity.

Nvidia ( NVDA ) declined 2.3%. The company is expected to

reveal details of its latest AI chip at its annual software

developer conference.

Tesla fell 4.2% after brokerage RBC trimmed its

price target on the EV maker's stock, flagging the company is

losing market share in China and Europe.

Other megacaps slid, with Amazon.com ( AMZN ) losing 1.8%

and Meta down 4.3%.

Investors flocked to safe-haven assets, with gold

trading at a record high, after crossing $3,000 per ounce for

the first time last week.

U.S.-listed stocks of gold miners such as Barrick Gold

rose 1% and Gold Fields gained 3.3%.

On the data front, manufacturing production increased more

than expected in February.

Declining issues outnumbered advancers for a 2.35-to-1 ratio

on the NYSE and a 2.53-to-1 ratio on the Nasdaq.

The S&P 500 posted four new 52-week highs and three new

lows, while the Nasdaq Composite recorded 25 new highs and 105

new lows.