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* Oil prices spike on tight supplies, upbeat OPEC

* Oracle down after downbeat forecast, Q1 revenue miss

* WestRock jumps on Smurfit Kappa merger

* Indexes: Dow up 0.06%, S&P down 0.34%, Nasdaq down 0.64%

Sept 12 (Reuters) - The S&P 500 and Nasdaq fell on Tuesday as a jump in oil prices deepened worries about persistent price pressures ahead of crucial inflation readings this week, while Oracle slumped on downbeat forecast and results.

Oil prices jumped more than 1% on Tuesday, building on a recent rally and stoking worries over sticky inflation in the aftermath of strong economic data, clouding the chances of an end to U.S. monetary policy tightening.

"People are a little bit worried about energy prices picking up pretty aggressively in recent weeks and that creates some concerns as we look forward to November," said Thomas Hayes, chairman at Great Hill Capital LLC.

Investors now keenly await August consumer prices data due on Wednesday and producer prices reading scheduled for Thursday to gauge the outlook for U.S. interest rates ahead of the Federal Reserve's monetary policy outcome on Sept. 20.

"If inflation keeps on increasing like this, which is what's anticipated, the Fed might hold interest rates higher for longer," said Michael Matousek, head trader at U.S. Global Investors Inc.

Traders still see a 93% chance of rates remaining at the current levels in September and a near 56% likelihood of a pause in November, as per the CME FedWatch Tool.

Investors will also monitor the European Central Bank's policy decision on Thursday, where it is seen holding rates after nine consecutive hikes.

Weighing down the S&P 500, cloud-services provider Oracle dropped 11.3% to its lowest intra-day level in three months, after forecasting current-quarter revenue below targets and narrowly missing first-quarter expectations.

While higher oil prices fanned inflation fears, they lifted energy stocks by 2% to lead gains among major S&P 500 sector indexes.

Megacaps Amazon.com, Microsoft and Meta platforms dropped between 1.3% and 1.6%, respectively, also pressured by a rise in U.S. Treasury yields.

Apple lost 1.4% on a report that China's Huawei Technologies has raised the second-half shipment target for its Mate 60 series smartphone by 20%.

Investors also awaited new iPhone 15 lineup launch amid uncertainty over market access in China and intensifying competition.

At 11:37 a.m. ET, the Dow Jones Industrial Average was up 21.31 points, or 0.06%, at 34,685.03, the S&P 500 was down 15.17 points, or 0.34%, at 4,472.29, and the Nasdaq Composite was down 89.58 points, or 0.64%, at 13,828.31.

WestRock jumped 4.3% on agreeing to merge with Europe's Smurfit Kappa to create the world's largest listed paper and packaging company worth nearly $20 billion.

Advance Auto Parts lost 6.4% after S&P Global downgraded the auto parts retailer's credit and debt ratings from investment grade (BBB-) to junk (BB+).

Zions Bancorp jumped 6.5% after the U.S. regional lender posted a slight increase in its monthly net interest income growth.

Advancing issues outnumbered decliners by a 1.05-to-1 ratio on the NYSE and by a 1.06-to-1 ratio on the Nasdaq.

The S&P index recorded 10 new 52-week highs and 13 new lows, while the Nasdaq recorded 32 new highs and 135 new lows. (Reporting by Ankika Biswas and Shristi Achar A in Bengaluru; Editing by Arun Koyyur and Vinay Dwivedi)