Stocks up and down amid jitters on key interest rate

A day after their biggest gain in six weeks, U.S. stock indexes mostly fell Tuesday as oil prices kept sliding and investors fretted over when the Federal Reserve will raise a key borrowing rate.

Losses were small, but spread across industries. The S&P 500 fell 6.99 points, or 0.3 percent, to 2,074.20. The Dow Jones industrial average lost 128.34 points, or 0.7 percent, to 17,849.08, after jumping 228 points the day before. The Nasdaq composite edged up 7.93 points, or 0.2 percent, to 4,937.43.

Low rates have helped stocks soar over the past six years. The Fed will release a policy statement on rates Wednesday.

New Facebook app allows electronic money transfers

Facebook’s Messenger app will soon let you send your friends money, the latest in a crowded field of services aimed at an increasingly wireless and cashless generation.

Services including PayPal, its Venmo unit and the disappearing-photo app Snapchat let you beam money to friends and family using smartphones linked to bank accounts or credit cards.

Facebook’s entry, announced Tuesday, is free, works with debit cards and is available on Apple and Android mobile devices and on desktop computers.

The world’s largest social network, which will process the payments, emphasized the service’s security features.