US STOCKS-Wall St dips, earnings on deck from Apple and Twitter

* Fed began two-day monetary policy meeting on Tuesday

* McDonald's, Verizon (NYSE: VZ - news) fall on weak results

* Caterpillar (NYSE: CAT - news) , Texas Instruments (Sao Paolo: TEXA34F.SA - news) rise on upbeat earnings, forecast

* Indexes: Dow -0.33 pct, S&P -0.16 pct, Nasdaq +0.07 pct (Updates to afternoon trading)

By Noel Randewich

July 26 (Reuters) - U.S (Other OTC: UBGXF - news) . stocks dipped on Tuesday as Federal Reserve policymakers kicked off a two-day interest rate meeting and investors braced for quarterly scorecards from Apple (NasdaqGS: AAPL - news) and Twitter (Xetra: A1W6XZ - news) .

It was the second day of declines after a recent rally to consecutive record highs on the S&P 500 that has stretched price-to-earnings multiples to levels that some investors say presumes that companies will beat second-quarter estimates.

Six of the 10 major S&P sectors declined, led by a 1.5 percent drop in the telecom services index. Verizon Communications shares fell 2 percent after the company's subscriber numbers fell below estimates.

Caterpillar's shares jumped 4.2 percent to touch a year high after the company's quarterly earnings beat expectations.

The Federal Reserve began a two-day meeting and while it is not expected to raise U.S. interest rates, investors will be watching for hints about when the U.S. central bank might make a move.

A set of strong economic data, including Tuesday's housing report, could strengthen the case for the Fed to raise rates earlier than the market anticipates.

"The real thing I'm going to be looking for is, is there a tip of the hat to a potential rate increase in September?," said Brad McMillan, chief investment officer at Commonwealth Financial Network.

At 2:23 p.m. (1823 GMT), the Dow Jones industrial average was down 0.33 percent at 18,431.46 and the S&P 500 had lost 0.16 percent to 2,164.97. The Nasdaq Composite added 0.07 percent to 5,100.96.

Shares (Berlin: DI6.BE - news) of Apple, the world's largest publicly traded company, dipped 0.65 percent ahead of its quarterly report after the bell, when investors will be looking for new details about how much iPhone sales are likely to decline in 2016.

Twitter has been struggling with sluggish user growth that has trailed Facebook (NasdaqGS: FB - news) and other social media competitors and its stock was down 1.5 percent ahead of its report.

McDonald's sank 4.4 percent after reporting worse-than-expected quarterly sales at established U.S. restaurants. The stock weighed the most on the Dow.

Texas Instruments jumped 9 percent after its current-quarter forecast beat analysts' estimates. The stock provided the biggest boost to the S&P 500.

Advancing issues outnumbered declining ones on the NYSE by a 1.42-to-1 ratio; on Nasdaq (NasdaqGS: NDAQ - news) , a 1.40-to-1 ratio favored advancers.

The S&P 500 posted 50 new 52-week highs and no new lows; the Nasdaq Composite recorded 107 new highs and 23 new lows. (Additional reporting by Yashaswini Swamynathan in Bengaluru; Editing by James Dalgleish)