UPDATE 1-European bourses cautiously wait for Fed update on tapering

* Stoxx 600 down 0.2 pct

* All eyes on Fed meeting

Financials edge up

* Ocado falls after Q3 results (Adds quotes, more company news)

By Julien Ponthus

LONDON, Sept 19 (Reuters) - European shares opened slightly lower on Tuesday as traders awaited clues from a Federal Reserve meeting on its plans to move towards unwinding its $4.2-trillion portfolio of Treasuries and mortgage-backed securities.

Despite Wall Street reaching new highs yet again, shares in Europe followed Asia's overnight caution with the pan-European STOXX index down 0.2 percent, but still in range of six-week highs.

"As the FOMC (Federal Open Market Committee) convenes and starts its two-day meeting, markets will probably remain somewhat muted awaiting tomorrows (Wednesday's) decision", Rabobank's analysts said in a morning note.

Financials were trading in positive territory, as monetary tightening typically benefits lenders. The European banking index was up 0.1 percent with HSBC at the top of the list with a 1-percent rise.

Most sectors posted very limited losses or gains.

"The prospect of the Fed meeting is triggering little worries as the market has already digested the idea that the reduction of the balance sheet will be done on homeopathic dosage, thereby limiting negative impacts on stocks", wrote Saxo Bank's economist Christopher Dembik, noting that geopolitical concerns were also easing off.

A steady flow of corporate news fueled strong price swings on a number of stocks.

British online grocer Ocado topped Europe's losers list with a 5.5-percent fall after the firm reported third-quarter results, saying short-term costs could increase due to investment in a new distribution centre.

Heineken retreated 4.5 percent after Fomento Economico Mexicano (Femsa) sold a 5.24-percent stake in the world's second largest brewer for about 2.5 billion euros ($3 billion).

Morgan Stanley cut its rating for Hugo Boss to underweight, prompting a 3.8-percent fall for the German fashion group.

On the M&A front, Eurofins got a boost from the acquisition of EAG Laboratories in North America and rose 4.1 percent.

Shares in Solvay didn't benefit from the announcement of the sale of its polyamides business to BASF for 1.6 billion euros. The Belgian company lost 1.1 percent while Germany BASF was 0.1 percent down.

Shares in Solvay, which bought Frances Rhodia for 3.4 billion in 2011, remain however close to their 2015 highs of 132 euros per share.

Clariant edged up 0.3 percent as news emerged the hedge funds fighting the Swiss chemical firms planned $20 billion merger with Huntsman Corp built a 15.1 percent stake. (Editing by Andrew Heavens)