Prices of crude oil and copper — two of the biggest industrial commodities — remained weak amid uncertainties posed by fresh elections looming in Greece and a cut in the credit ratings of 16 Spanish banks by Moody's.

Leaders of major industrial economies meet this weekend to try to head off a full-blown crisis in Europe where fears are growing that Greece could leave the euro zone bloc, threatening the future of the common currency.

"Given how critical the situation is in Europe at present, policy makers may well feel the need to come up with something to soothe the markets and the possibility of that might lead to some book squaring ahead of the weekend," Fastmarkets said in a note.

Worries about a slowing economy in China — the world's largest metals importer and a giant consumer of many other raw materials — further clouded the demand outlook for commodities, analysts said.

Oil and copper prices fell 4 percent on the week.

The front-month contract for U.S. crude oil was about $2 away from its $90 per barrel support. Brent crude in London was less than $2 away from its $105 support.

Copper futures in London had their biggest weekly decline since December, settling below the $8,000 a tonne level, which was critical for the confidence of market bulls.

While many expected prices to test new lows in coming days, some braced for an odd rebound that could surprise.

"Next week is a tough call, but my gut feeling is that we'll see slightly higher prices because we've gone too far on the downside," said Stephen Briggs, metals strategist for BNP Paribas in London.

The 19-commodity Thomson Reuters-Jefferies CRB index edged higher after the relative outperformance of wheat, gold and a few other markets such as corn and cocoa.

On a weekly basis, however, the CRB was headed for its third week of declines, weighed down by the multi-month lows in oil and copper.

WHEAT SIMMERS ON HEAT WAVE

U.S. wheat futures were on course to add about 16 percent to prices for the week as hot and dry weather kept fears simmering about crop losses in the U.S. Plains and Russia.

"Wheat is a weather market right now," said Jack Scoville, analyst for brokers TPFG in Chicago.

Crop experts said the promise of a bumper harvest for U.S. hard red winter wheat was eroding by the hour as scorching weather and high winds in important growing areas of the U.S. Plains sapped soils of needed moisture.

Benchmark wheat for July on the Chicago Board of Trade was hovering around $6.96 a bushel, up nearly 39 cents, or almost 6 percent for the day.

For the week, wheat was up almost $1 a bushel, or 16 percent. Reuters data showed that was the biggest weekly gain since 1996 for a front-month CBOT wheat contract on a spot continuation basis.

In gold's case, Friday's uptick lifted the precious metal to its strongest week in a month.

The spot price of gold, which tracks trade in bullion, hovered just below $1,580 an ounce, up nearly $20 on the day. After a woeful month that saw gold down three-fourths of the time and breaching various technical low points as investors sold the precious metal to cover losses elsewhere, the market popped on Thursday, rising nearly $35.

The two-day rally has put the spot price of gold up 0.7 percent for the week — its most since the week of mid-April — after accounting for sharp losses in the first three sessions of the week.