U.S. stock index futures rose on Tuesday, erasing earlier declines, as Spanish bond yields eased on optimism Germany's top court will approve the euro zone's new bailout fund, enabling a more flexible use of the latest rescue plan.

The German Constitutional Court will consider whether Europe's new bailout plan and budget rules are compatible with national law in a process influencing not just how to tackle the euro zone debt crisis, but how much deeper European integration can go.

German Finance Minister Wolfgang Schaeuble told the court on Tuesday that any significant delay in approving the permanent bailout fund could fuel financial market turbulence.

Spanish bond yields backed off the 7 percent level, which has forced other countries to seek a bailout, on hopes the plan will be approved as a lengthy delay could once again rattle markets.

The FTSEurofirst 300 <.FTEU3> index was up 1 percent in a broad rally, putting the index on track for its first gain in the past five sessions. <.EU>

"This has been an incredibly slow process with lots of stops and starts - it has made their attempts less effective because they seem constantly open to challenge somewhere," said Rick Meckler, president of investment firm LibertyView Capital Management in New York.

"It's just a more difficult process, it doesn't mean it can't come to the same conclusion at the end of the day but it certainly is taking a very long time and the markets are reflecting that you are never quite sure this is the step that is needed."

Futures were initially lower after data in China showed import growth slowed sharply in June to 6.3 percent, well short of the 12.7 percent increase forecast. Europe is the largest trade partner for China and the data underscored the effect the euro zone debt crisis has had on growth.

S&P 500 futures rose 4 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 61 points, and Nasdaq 100 futures added 11.25 points.

Alcoa Inc late on Monday kicked off quarterly earnings season with revenue and profit that beat Wall Street's expectations even though prices for its aluminum are at nearly two-year lows, and it forecast growing demand in the aerospace and auto sectors. Shares of the aluminum giant rose 0.8 percent to $8.83 in premarket trade.

Intel Corp will spend more than $4 billion on up to 15 percent of ASML and bankroll the Dutch company's research into costly next-generation chipmaking technology, a major vote of confidence in the European firm. U.S.-listed shares of ASML jumped 9.7 percent to $53.15 and Intel dipped 0.9 percent to $25.94 in premarket.

Advanced Micro Devices tumbled 9.1 percent to $5.11 in premarket after the chipmaker slashed its outlook for second-quarter revenue after seeing disappointing sales in China and Europe.

Asian shares were lower on the China data.

(Reporting by Chuck Mikolajczak; Editing by Chizu Nomiyama)