U.S. stocks were set to open slightly higher on Monday after posting heavy losses last week as a bounce-back in commodities was overshadowed by concerns over European debt.

Futures pared gains as Standard & Poor's cut Greece's debt rating, saying there is increased risk Athens will restructure its private debt.

The rating cut weakened the euro against the U.S. dollar, shaving gains off commodities and reducing some risk appetite that earlier had lifted futures.

The concerns over Greece and the action in the euro are going to dominate the action today, said Ryan Detrick, senior technical strategist at Schaeffer's Investment Research.

S&P 500 futures edged up 1 point and were flat in terms of fair value, a formula that evaluates pricing by taking into account interest rates, dividends and time to expiration of the contract. Dow Jones industrial average futures gained 15 points and Nasdaq 100 futures added 8.50 points.

Schaeffer's Detrick said 1,340 and 1,333 are key levels on the S&P 500 that should provide strong support and entice buyers.

If those levels do give way, it would mean Europe is trumping an overall good earnings season, he said.

Brent and U.S. crude futures rose almost 2 percent after gaining more than 3 percent earlier. Copper and gold gained 0.8 percent after earlier trading more than 1 percent higher each.

Shares of mining company Freeport-McMoRan Copper & Gold Inc gained 1.3 percent in premarket trading to $50.83.

The iShares Silver Trust exchange-traded fund jumped 4.4 percent to $35.99 before the open, with more than 5.6 million shares traded.

Among companies reporting earnings Monday, SYSCO Corp gained 5.3 percent to $30.01 premarket. Results from Sempra Energy are also expected. About 70 percent of S&P 500 companies that have reported results have beaten expectations.

Relatively low volume so far this year could see a further decline as Citigroup Inc's 1-for-10 reverse stock split comes into effect Monday. Citi shares have recently accounted for about 6 percent of composite volume.

Citi shares traded at $44.93 after closing at $4.52 on Friday.

Last week, the Dow Jones industrial average <.DJI> lost 1.3 percent, the Standard & Poor's 500 <.SPX> fell 1.7 percent and the Nasdaq Composite <.IXIC> dropped 1.6 percent.

Despite last week's losses, the S&P 500 held above important technical levels, with the week's low just below 1,330 and Friday's close above 1,340.

(Reporting by Rodrigo Campos; Editing by Kenneth Barry)