U.S. stocks retreated as tumbling oil prices weighed on energy and raw-material companies, sparking a selloff after equities posted their biggest one-day gain in three months.

The S&P 500 fell 0.7 percent to 2,077.15 at 4 p.m. in New York, trimming an earlier drop of as much as 1.2 percent, after jumping 2.1 percent on Friday.

Crude prices extended losses after falling 2.7 percent Friday amid speculation a record global glut will be prolonged as the Organization of Petroleum Exporting Countries effectively abandoned its long-time strategy of limiting production to control prices. West Texas Intermediate futures fell 5.8 percent Monday to $37.65 a barrel, the lowest close since February 2009.

Oil's plunge of more than 40 percent in the past year has hampered recoveries in the U.S. and Europe as capital spending has waned and inflation has remained below central-bank targets.

U.S. stocks are coming off their most volatile week since the summer as investors were faced with releases from the Labor Department, the European Central Bank and speeches by Federal Reserve Chair Janet Yellen. The S&P 500's rally on Friday left it little changed for a second straight week after a report showed U.S. employers added more jobs than forecast in November, increasing speculation that the economy is strong enough to withstand higher borrowing costs -- something that Yellen has signaled.

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Traders are pricing in a 78 percent chance of liftoff before the Fed's interest-rate decision on Dec. 16. Investors will have little data this week to assess the strength of the economy. Reports on retail sales, a measure of producer prices and the University of Michigan's preliminary consumer sentiment index are due, though not until the end of the week.

The selloff in equities today extended a stretch of whipsaw trading to a fifth day. The main U.S. equity index moved at least 1 percent in the previous four days, the longest stretch since August, kicking off what is usually the second-best month of the year. The S&P 500 has not had back-to-back gains in more than a month.