LONDON   - Commodities faced a mixed week as traders assessed the supply outlook and after Federal Reserve chief Ben Bernanke dented hopes of stimulus measures any time soon in the world’s biggest economy.

Bernanke, speaking at the Fed’s annual global Jackson Hole gathering of central bankers on Friday, called the US economic situation unsatisfactory but offered no new promises of intervention.

However, he confirmed that the Fed would move “if economic conditions warrant,” as he labelled the labor market stagnation “a grave concern.”

The European Central Bank meanwhile doused hopes of extra stimulus after its president Mario Draghi pulled out of attending Jackson Hole. Market hopes had been building that central banks could implement more quantitative easing (QE) -- whereby new cash is created and pumped into the economy.

OIL: Market sentiment was dictated by speculation over additional central bank stimulus and the potential release of strategic crude stocks, as well as mixed data and hurricane-linked US supply concerns.

Fears about disruption to supply from the US Gulf from Hurricane Isaac had lifted prices at the start of the week but, in the end, those concerns proved unfounded.

“The markets have been torn this week by rumours of a stockpile release and mixed signals from the economy after US GDP was revised up,” said analyst Tom Pering at British-based energy consultancy Inenco.

“Despite this, oil is ready for a fall and unless the Federal Reserve or the European Central Bank indicates any positive policy measures, this trend is likely to continue next week.

“Many investors feel oil is over-priced and are looking for falls. Meanwhile, although the disruption caused by Hurricane Isaac was minimal, this has still kept a dampener on prices.”

The Gulf of Mexico is the hub of US offshore energy production, accounting for 23 percent of crude oil output and 7.0 percent for natural gas.

Oil prices were also pressured by a call from the Group of Seven (G7) nations for producers to increase output.

G7 finance ministers said in a statement issued Tuesday that crude supply needed to be increased as higher prices posed “substantial risks” to the global economy.

They also suggested that leading industrial economies were ready to tap into global strategic oil reserves to keep price pressure down.

By late Friday on London’s Intercontinental Exchange, Brent North Sea crude for delivery in October eased to $114.08 a barrel from $114.79 a week earlier.

On the New York Mercantile Exchange, West Texas Intermediate (WTI) or light sweet crude for October stood at $96.26 a barrel compared with $96.83 the previous week.

PRECIOUS METALS: Gold briefly rebounded to a four-month high as traders focused on the possibility of more asset purchases by the Fed. However, the precious metal finished the week on a flat note.

“The fact that the Fed Chairman stated that he ‘wouldn’t rule out further asset purchases’ saw the yellow metal bounce back again,” said CMC Markets analyst Michael Hewson.

By late Friday on the London Bullion Market, gold had eased to $1,648.50 an ounce from $1,667 a week earlier.

Silver rose to $30.52 an ounce from $30.37.

On the London Platinum and Palladium Market, platinum decreased to $1,517 an ounce from $1,537.

Palladium fell to $623 an ounce from $643.

BASE METALS: Prices slid in line with most other commodities. “Metals continued to consolidate in choppy conditions,” noted analyst William Adams at Fast Markets.

By late Friday on the London Metal Exchange, copper for delivery in three months dropped to $7,563 a tonne from $7,660 a week earlier.

Three-month aluminium dipped to $1,877 a tonne from $1,918.

Three-month lead fell to $1,952 a tonne from $1,967.

Three-month tin sank to $19,450 a tonne from $20,325.

Three-month nickel declined to $15,905 a tonne from $16,531.

Three-month zinc decreased to $1,824 a tonne from $1,882.

SUGAR: Sugar hit another two-year low in London at $544.50 a tonne on the prospect of abundant Brazilian supplies.

By Friday on LIFFE, London’s futures exchange, the price of a tonne of white sugar for delivery in October slid to $547.80 from $558.20 a week earlier.

In New York on NYBOT-ICE, the price of unrefined sugar for October dropped to 19.65 US cents a pound from 20.20 cents.

COCOA: Prices soared to their highest levels since November 2011, propelled by weather concerns in key producing African nations.

“Worries about the drier than normal conditions in the growing regions of West Africa, generated much of the upward price momentum,” noted trade publication the Public Ledger.

By Friday on LIFFE, cocoa for delivery in December rallied to £1,704 a tonne from £1,580 a week earlier.

On the NYBOT-ICE, cocoa for December rose to $2,607 a tonne from $2,382.

COFFEE: Coffee prices also increased in value.

By Friday on NYBOT-ICE, Arabica for delivery in December rose to 165 US cents a pound from 162.15 cents a week earlier.

On LIFFE, Robusta for November increased to $2,069 a tonne from $2,030.

RUBBER: Prices flattened as many traders stayed on the sidelines amid demand concerns and a report that rubber producer Thailand had decided against further moves to stabilise the market.

The Malaysian Rubber Board’s benchmark SMR20 inched upwards to 253.45 US cents a kilo from 252.80 cents the previous week.