Oil hit its lowest since early June on Tuesday, as concern about the economic outlook dented commodities, while bonds, currencies and stocks traded cautiously ahead of a number of key central bank decisions and a slew of major corporate earnings reports.

Brent crude futures fell to a low of $79.34 a barrel, as worry over Chinese energy demand outweighed any concern about tensions in the Middle East or Venezuela.

Copper and iron ore prices fell, and zinc and aluminium slipped to multi-month lows, while there was little by way of support from China's Politburo, which at its July meeting announced no new detailed efforts to boost the economy.

"The consensus is that the U.S. economy is going to be softer this quarter and maybe next quarter as well and you can't really rely on the euro area to offer any compensation for that. China has got its own problems and doesn't look like it's going to snap into gear," Daiwa Capital economist Chris Scicluna said.

"Understandably, we might have been hoping for the global economy to be gaining traction and momentum to be picking up at this stage in the cycle, but it looks like maybe things are coming off the boil a bit," he said.

U.S. stock futures rose 0.2%, suggesting a modest uptick in the benchmark indices later on .

The MSCI All-World index, which is heading for a third straight monthly gain in July, was flat, while in Europe, London's FTSE 100 was the worst-performing index in the region, as basic resources stocks slid and top spirits maker Diageo hit a 4-1/2 year low following a profit miss.

Preliminary euro zone data showed economic growth in the single currency bloc expanded at an annual rate of 0.6% in the second quarter of this year, above forecasts for a reading of 0.5%. A separate report showed the German economy unexpectedly contracted in the second quarter, but this had little bearing on expectations for interest rates.

German 10-year Bund yields were steady around 2.358%.

'CALM BEFORE THE STORM'

Interest rates remain front and centre. Japanese government bond yields edged lower with the 10-year JGB yield ending down 3 basis points at 0.995%. Ten-year U.S. Treasury yields eased 1 bp to 4.1685%.

"The term 'calm before the storm' has been heard across the floors," said Chris Weston, head of research at Pepperstone in Melbourne. "This is a day for position management and to review broad exposures."

Markets are pricing almost no chance of a U.S. rate cut this week, but have fully priced a 25-basis-point reduction in the Fed Funds rate for September and so expect policymakers to sound dovish.

In Japan, a broader range of outcomes is on the table, with markets pricing a nearly 60% chance of a 10-basis-point rate hike and expecting to hear about how the Bank of Japan plans to edge its way out of an enormous bond-buying programme.

The dollar and yen drifted, but kept in fairly compact ranges after recent breakout moves.

The euro edged up 0.12% to $1.0833, while the yen , which has rebounded sharply from a 38-year low of 161.96 per dollar hit early in July, came under pressure, leaving the dollar/yen pair up 0.46% at 154.725 per dollar.

"We are at an interesting intersection for yen here," said Nathan Swami, head of currency trading at Citi in Singapore, with this week's central bank meetings possibly sketching a shift in the rates outlook and the yen's trajectory.

"It is too early to tell if the factors driving yen weakness have changed permanently. For now, this seems more like a short-term correction to the USD/JPY higher trend, but we feel there is downside risk that needs to be priced into a trade."

Later in the day, Microsoft and chipmaker AMD will report earnings after the bell in New York, while preliminary CPI data is due in Germany and Spain.

Australian inflation data will also be released on Wednesday and the Bank of England is priced for a roughly even chance of a rate cut at its policy meeting on Thursday.

(Editing by Sherry Jacob-Phillips, Sharon Singleton and Ros Russell)