U.S. stock index futures rose on Monday as investors welcomed details of a fiscal aid package for Greece and focused on a merger that would create the world's largest airline.

European countries agreed to a 110 billion-euro ($146.5 billion) aid package for debt-laden Greece, the biggest ever financial bailout of a country. But European stocks fell on concerns that the package may face political obstacles and on doubts that Greece can implement the tough austerity measures it has promised in exchange.

UAL Corp , parent of United Airlines, will buy Continental Airlines Inc for $3.2 billion, in a deal that would form the world's largest airline.

Warren Buffett on Sunday intensified his feisty defense of a controversial mortgage transaction marketed by Goldman Sachs Group Inc , saying the investment bank's behavior does not warrant public fury. Buffett also said he is seeing signs of improvement in the economy, especially in manufacturing, though he said it will take another year for a sustainable housing recovery to take hold.

Due later Monday are March figures for personal consumption expenditures, personal income and construction spending data and ISM manufacturing data for April. The median Reuters forecast of 32 economists for the ISM's manufacturing index is 60.0, up from 59.6 in March. The market will also keep a close eye on car sales for April.

Clorox Co , Loews Corp and Anadarko Petroleum Corp are scheduled to report earnings on Monday.

Energy shares will be in the spotlight again as the huge oil slick caused by an underwater leak continued to creep toward the U.S. Gulf Coast on Monday. The Obama administration pressed energy giant BP Plc to stem the oil gushing from its ruptured offshore well. BP's U.S.-traded shares fell about 2 percent in premarket trades.

China on Sunday raised the proportion of deposits that lenders must keep in reserve at the central bank, another step in the country's campaign to remove excess cash in the economy.

Investors were also digesting news of a failed car bombing in New York. Investigators combed through security video and other evidence on Monday in the hunt for suspects and officials expressed optimism that the culprits will be found.

U.S. stocks tumbled on Friday to close out the worst week since January as news of a criminal probe into Goldman Sachs unnerved investors already anxious about the prospects for heavy regulation from Washington. But the three major U.S. stock indexes have racked up gains for the last three months.

(Reporting by Angela Moon; Editing by Padraic Cassidy)