SHANGHAI, July 27 (Reuters) - Mainland China and Hong Kong stocks edged lower on Wednesday as caution kicked in ahead of the outcome of U.S. Federal Reserve's policy meeting later in the day.

** The Fed's announcement is due at 1800 GMT and the U.S. central bank is widely anticipated to raise interest rates by another 75 basis points to combat inflation. Investors are also eyeing any further comments on monetary tightening.

** At the midday break, the Shanghai Composite index eased 0.09% at 3,274.37 points, while the blue-chip CSI300 index fell 0.46% to 4,226.53 points.

** The financial sub-index dropped 0.34%, the consumer staples sector lost 0.92%, and the healthcare sub-index fell 1.59%.

** The smaller Shenzhen index inched higher by 0.14%, the start-up board ChiNext Composite index was weaker by 0.21%, and Shanghai's tech-focued STAR50 index gained 0.32%.

** In Hong Kong, the benchmark Hang Seng Index fell 1.51% to 20,590.46, while Chinese H-shares listed in Hong Kong dropped 1.67% to 7,064.98.

** "Beyond the Fed's decision, global outlook and sentiments likely will remain suppressed by U.S. and euro zone growth worries and financial stability risks in China," said strategists at DBS in a note.

** In China, investors continued to be worried about the property sector, after Country Garden Holdings Co Ltd said on Wednesday it planned to raise HK$2.83 billion from a share sale, raising proceeds for refinancing existing offshore debt, general working capital and future development purposes.

** The real estate index fell 0.09%, while mainland developers listed in Hong Kong plunged 5.72% by noon.

** Separately, China's key money rate fell to a new 1-1/2-year low on Wednesday, pressured by ample liquidity as the economy rebounds from a sharp COVID-induced slump. (Reporting by the Shanghai Newsroom; editing by Uttaresh.V)