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* Apple expected to launch four new iPhone models at virtual event
* Amazon rises as two-day 'Prime' shopping event gets underway
* BlackRock rises after results
* Disney jumps as it restructures its media business
* Indexes down: Dow 0.38%, S&P 0.35%, Nasdaq 0.26% (Updates to open)
By Medha Singh and Shivani Kumaresan
Oct 13 (Reuters) - Wall Street's main indexes fell on Tuesday after a four-day winning streak as a pause in Johnson & Johnson's COVID-19 vaccine trials spurred concerns about a full economic rebound from the coronavirus-led downturn.
Johnson & Johnson raised its annual profit forecast, but its shares dropped 1.2% as it suspended clinical trials following an unexplained illness in a study participant, possibly delaying one of the most closely watched efforts to contain the global pandemic.
Some of the worst-hit companies due to the pandemic - cruise line operators Carnival Corp, Norwegian Cruise Line Holdings and hotel operator Wynn Resorts Ltd - were among the top losers on the S&P 500.
"It reminds those betting on a vaccine that it's probably not as clear cut that it's just on the horizon as the administration makes it to be," said Rick Meckler, a partner at Cherry Lane Investments, a family investment office in New Vernon, New Jersey.
Adding to the negative tone, U.S. House Speaker Nancy Pelosi rejected President Donald Trump's latest offer on COVID-19 stimulus, in the latest sign that a bipartisan deal on coronavirus relief remains unlikely ahead of the November election.
Hopes of more U.S. fiscal stimulus and a rally in technology heavyweights led stocks higher on Monday, bringing the benchmark S&P 500 and the tech-heavy Nasdaq within 2% of their record highs hit in September after a pullback last month.
Apple Inc gave up early gains to fall 1.9% ahead of a virtual event starting 1 p.m. ET (1700 GMT) where it is widely expected to unveil four new iPhones.
Shares of Amazon.com Inc, which have already surged 86% this year, added 0.2% as it began 48 hours of promotions as part of "Prime Day" in an early start to the holiday shopping season.
Kicking off third-quarter earnings season, JPMorgan Chase & Co and Citigroup surpassed analyst estimates for quarterly profit on a surge in trading revenue. However, their shares fell 0.3% and 1.6%, respectively.
Bank stocks slipped 0.6%. The index has widely underperformed the broader market in 2020 and analysts expect the sector's earnings to take years to make a full recovery as interest rates remain near record lows.
Overall, analysts expect third-quarter earnings for S&P 500 firms to slide 20.7% from a year earlier, smaller than a 31% tumble in the prior quarter.
At 9:54 a.m. ET, the Dow Jones Industrial Average was down 109.40 points, or 0.38%, at 28,728.12, the S&P 500 was down 12.27 points, or 0.35%, at 3,521.95, and the Nasdaq Composite was down 30.51 points, or 0.26%, at 11,845.75.
Walt Disney Co jumped 3.5% as it restructured its media and entertainment businesses to accelerate growth of Disney+ and other streaming services.
The world's largest asset manager BlackRock Inc rose 3.7% after reporting better than expected quarterly profit as the recovery rally in global financial markets boosted asset values and pulled in more investor funds.
Declining issues outnumbered advancers for a 2.54-to-1 ratio on the NYSE and for a 1.98-to-1 ratio on the Nasdaq.
The S&P index recorded 23 new 52-week highs and no new low, while the Nasdaq recorded 41 new highs and six new lows. (Reporting by Medha Singh in Bengalurua and Shivani Kumaresan; Editing by Shounak Dasgupta and Saumyadeb Chakrabarty)