US STOCKS-Wall St inches higher ahead of Fed policy meeting

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* Boeing extends losses as Ethiopia crash data scrutinized

* Facebook drops on regulatory fears, broker downgrade

* Apple rises after new iPad launch

* Goldman, Citi gain on German bank deal

* Indexes up: Dow 0.12 pct, S&P 500 0.29 pct, Nasdaq 0.28 pct (Updates to late afternoon; changes dateline, byline)

By Stephen Culp

NEW YORK, March 18 (Reuters) - Wall Street edged higher on Monday as declines in Boeing and Facebook held gains in check and investors eyed this week's Federal Reserve meeting for affirmation of the central bank's commitment to "patient" monetary policy.

Coming on the heels of the S&P 500's best week since November, the benchmark index currently hovers about 3.4 percent below its all-time high reached in September. All three major U.S. indexes were in positive territory.

"People were so pessimistic around year-end, but the market has since had a tremendous rebound and now we're in a wait-and-see phase," said Peter Tuz, president of Chase Investment Counsel in Charlottesville, Virginia.

The Dow's nominal advance was hindered by Boeing Co, which fell 2.0 percent as the company faced increasing scrutiny regarding safety of its 737 MAX planes following a fatal crash in Ethiopia on March 10. The world's largest plane maker extended last week's 10.3 percent decline and was the heaviest weight on the blue-chip index.

On Tuesday the U.S. Federal Reserve's two-day policy meeting begins. Investors expect the central bank to reinforce its "patient" approach toward further interest rate hikes.

"Whatever the Fed says could move the market," Tuz added. "We think that (the Fed is) on hold for the time being."

Brexit helped curbed investor optimism as Great Britain's speaker of Parliament warned that Prime Minister Theresa May's deal would not be put to a vote unless it took a substantially different form.

The Dow Jones Industrial Average rose 31.79 points, or 0.12 percent, to 25,880.66, the S&P 500 gained 8.17 points, or 0.29 percent, to 2,830.65 and the Nasdaq Composite added 21.45 points, or 0.28 percent, to 7,709.98.

Of the 11 major sectors in the S&P 500, six were in the black, with energy and financial companies enjoying the biggest percentage gains.

The communications services sector was the largest percentage loser, weighed down by Facebook Inc.

Facebook's shares were down 3.1 percent after the deputy head of the European Commission said "at some point, we will have to regulate" big tech and social media companies to protect citizens and a top-rated Needham analyst downgraded the stock to "hold" from "buy."

Apple Inc helped push the tech sector higher when it surprised inventors with the launch of new iPad devices ahead of the company's expected March 25 launch of its content streaming service. The stock was up 0.9 percent.

Shares of Apple supplier Synaptics Inc swooned, dropping 22.1 percent after Mizuho downgraded the stock to "neutral" from "buy."

Goldman Sachs and Citigroup were up 2.2 percent and 1.2 percent, respectively, on news that the banks are helping Germany's two biggest lenders work on a potential merger worth more than $28 billion.

Advancing issues outnumbered declining ones on the NYSE by a 1.93-to-1 ratio; on Nasdaq, a 1.37-to-1 ratio favored advancers.

The S&P 500 posted 26 new 52-week highs and 1 new low; the Nasdaq Composite recorded 72 new highs and 23 new lows. (Reporting by Stephen Culp; Editing by Dan Grebler)