U.S. stock index futures fell on Tuesday as strength in the dollar pressured commodity prices and investors eyed a possible pullback in equity prices after a recent run-up.

The dollar hobbled near a three-year trough against a currency basket, undermined by loose U.S. monetary policy. But analysts said the fall looked overextended due to extreme short positioning.

The dollar index <.DXY>, measured against a basket of major currencies, was last up 0.4 percent.

Shares of mining company Freeport McMoRan Copper & Gold Inc and big metal exchange-traded funds for silver and gold, including the iShares Silver Trust and the SPDR Gold Trust , edged lower in premarket trading.

Brent crude fell 1.1 percent to $123.77 a barrel, and U.S. crude futures shed 1 percent to $112.40.

Basically, the dollar is a little bit higher, so that is weighing on risk this morning, said Peter Cardillo, chief market economist at Avalon Partners in New York.

Now we are seeing a little bit of divergence. We are beginning to see perhaps a little bit of a pullback in commodity prices and a dollar that might be in for a short-term bounce, so that cuts into risk.

S&P 500 futures fell 6.7 points and were below fair value, a formula that evaluates pricing by taking into account interest rates, dividends and time to expiration on the contract. Dow Jones industrial average futures dropped 51 points, and Nasdaq 100 futures lost 9.75 points.

The benchmark S&P 500 has risen 4.3 percent since April 18, when it hovered near the technical support level of 1,300.

Pfizer Inc

fell 1.1 percent to $20.80 premarket after the drugmaker reported quarterly results roughly in line with expectations and said it expects by the second half of the year to complete its review of which company businesses are appropriate to keep.

Other companies expected to post earnings include Comcast Corp , MasterCard Inc , Marathon Oil Corp and Cephalon Inc .

At 10 a.m. EST, the Commerce Department releases March factory orders. Economists in a Reuters survey expected a 1.9 percent rise, compared with a 0.1 percent drop in February.

European shares fell nearly 1 percent at midday as investors locked in profits following an eight-session winning streak for a key index, with declines in automakers and heavyweight miners weighing on the market. Asian shares were also dragged down by miners.

U.S. stocks slipped Monday as an early bounce from Osama bin Laden's death gave way to questions about the longevity of the market's recent rally.

(Reporting by Chuck Mikolajczak; editing by Jeffrey Benkoe)