A sign stocks may stall out was evident in the lackluster volume, in contrast with last week's selloff which occurred on heavy volume. Just 7.3 billion shares traded on the New York Stock Exchange, NYSE Amex and Nasdaq, well below last year's daily average of 8.47 billion.
"The market is clearly in a play-it-by-ear mode on what comes next, both in terms of the Middle East, the sustainability of this spike (in oil prices) and what, if sustained, this will do to the global economy," said Peter Boockvar, equity strategist at Miller Tabak + Co in New York.
Advertisement: Story continues belowBrent crude oil prices, which had jumped toward $US120 a barrel last week, eased to $US112. But investors were still jittery that the global economic recovery may be threatened if oil prices stay high.
Buffett, chairman of Berkshire Hathaway, spoke in his widely read annual letter to shareholders of the need for "major acquisitions," a sign stocks may be cheap.
The latest acquisition news came from Ventas, which plans to buy Nationwide Health Properties in a $US5.8 billion stock deal that strengthens Ventas' position as the biggest US owner of senior housing. NHP shares rose 9.7 per cent to $US42.74.
The Dow Jones industrial average was up 95.89 points, or 0.79 per cent, at 12,226.34. The Standard & Poor's 500 Index was up 7.35 points, or 0.56 per cent, at 1327.23. The Nasdaq Composite Index was up 1.22 points, or 0.04 per cent, at 2782.27.
The Nasdaq's gains were the smallest as Amazon.com fell 2.2 per cent to $US173.29 after UBS downgraded the online retailer, citing increased costs.
For the month, the Dow rose 2.8 per cent, the S&P rose 3.2 per cent and the Nasdaq gained 3 per cent.
Comments from Federal Reserve officials hinting they were ready to support the economy if necessary helped ease concern over the scheduled end of the Fed's $600 billion bond-buying program later this year.
New York Fed Bank President William Dudley said policymakers should be wary about withdrawing liquidity too quickly, while St. Louis Fed Bank President James Bullard would not rule out further use of the Fed's unorthodox tool for stimulus.
Data on Monday showed Midwest business activity rose more than forecast in February.
In addition, US incomes posted the largest increase since May 2009 last month. The jump partly reflected a payroll tax cut enacted last year.