Stock index futures were higher on Tuesday after better-than-expected results from Alcoa Inc and CSX Corp gave a promising start to the earnings season.

Late on Monday Alcoa, the first Dow component to report, posted second-quarter earnings that beat expectations, raising hopes of similarly strong results for other companies this season. Rail company CSX also posted a higher-than-expected profit.

Alcoa shares were up 4.5 percent to $11.36 in premarket trading while CSX closed Monday at $52.46.

Despite the strong earnings, gains could be capped by continued worries over the outlook for the euro zone after ratings agency Moody's Investor Service cut its rating on Portugal by two notches to A1. This follows rival agency S&P's two-notch cut of Portugal's debt in April.

S&P 500 futures rose 6.6 points and were above 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 gained 52 points, and Nasdaq 100 futures were up 13.5 points.

The earnings season picks up steam with the release of Dow component Intel Corp's report after the market closes on Tuesday, keeping tech stocks in focus. JPMorgan Chase & Co , Bank of America Corp and General Electric Co are also among the bellwethers on tap to report this week.

Economic data scheduled for Tuesday includes the U.S. Commerce Department figures for international trade at 8:30 EDT (1230 GMT) and the Federal budget due at 2 p.m. (1800 GMT).

U.S.-listed shares of BP Plc edged 0.7 percent higher to $37.01 in premarket trading as it prepared to try and seal off its runaway well with a new cap that it says could finally arrest the flow of oil spewing from the floor of the Gulf of Mexico.

The board of American International Group Inc is set to meet this week to consider the future of its AIA unit, with a public float seen as the most likely outcome, sources said on Tuesday.

In Europe, the pan-European FTSEurofirst 300 <.FTEU3> index of leading shares was up 1.5 percent, on track to close higher for the sixth straight day.

In Asia, equities were pressured by reports that China will not relax tougher property measures any time soon, a move which touched a nerve among investors who are already sensitive to how much China's economy is slowing.

The International Monetary Fund's chief reiterated on Tuesday that strong growth in Asia and Latin America made it unlikely that the global economy would suffer a double-dip recession.

U.S. stocks closed slightly higher in a light trading session on Monday, as cautious prevailed ahead of the release of Alcoa's and CSX's results.

(Editing by Chizu Nomiyama)