NEW YORK (CNN/Money) - Stocks clung to modest gains Monday, as a nearly 4 percent spike in oil unsettled investors ahead of the week's spate of big economic news.

Nasdaq and S&P futures pointed to a higher open Tuesday, when fair value is taken into account.

The Nasdaq composite (up 5.96 to 2,068.96, Charts) rose 0.3 percent and the Standard & Poor's 500 (up 2.71 to 1,200.82, Charts) index added 0.2 percent. The Dow Jones industrial average (up 9.93 to 10,522.56, Charts) ended little changed.

All three indexes had been higher earlier in the session.

Stocks had rallied more sharply in the late morning, finding momentum after a weak open. But that began to taper off in the midafternoon, coinciding with a spike in oil prices.

The price of the commodity had been up throughout the morning, but advanced more steadily in the afternoon ahead of Wednesday's OPEC meeting in Vienna. The international oil cartel will meet to discuss the possibility of boosting daily production quotas.

U.S. light crude for July delivery gained $2.08 to settle at $55.62 a barrel on the New York Mercantile Exchange, a rise of around 3.9 percent.

"It's just drifting up today, there's no one catalyst," said Tim Heekin, head of stock trading at Thomas Weisel Partners. "The calendar is loaded starting tomorrow," he added, noting that those reports would set the tone for the rest of the week.

This week promises to be busy for investors, with reads on producer prices and retail sales due Tuesday, consumer prices Wednesday and housing and manufacturing later in the week.

Tuesday also brings earnings from Best Buy (Research), and Lehman Brothers (Research). Lehman is the first of three Wall Street firms to report results this week.

Last week Federal Reserve Chairman Alan Greenspan made some upbeat comments about the strength of the economy and again pledged that the central bank would continue to raise interest rates at a measured pace.

Market participants will be looking to this week's economic numbers to reinforce these ideas.

"Economists are expecting a gradual slowdown in economic growth paired with a slowdown in inflation," said Jack Ablin, chief investment officer at Harris Trust. "That will allow the Federal Reserve to wind up its rate-hiking campaign."

"If the reports this week come in reasonably near estimates, that will reassure investors," he added.

May retail sales are expected to have fallen 0.2 percent, according to a consensus of economists surveyed by Briefing.com, after rising 1.4 percent in April. Sales excluding the volatile auto component likely rose 0.2 percent, analysts expect, after rising 1.1 percent in April.

The May Producer Price Index (PPI) is expected to have fallen 0.2 percent in the month, after rising 0.6 percent in April, economists expect. The so-called "core" PPI, which excludes volatile food and energy prices, is forecast to have risen 0.2 percent, after rising 0.3 percent in April.

Components Alcoa (up $0.30 to $27.40, Research), Hewlett-Packard (up $0.47 to $23.89, Research) and SBC Communications (up $0.28 to $23.91, Research) all rose, but failed to give the Dow much of a lift.

Dow component General Motors (down $0.06 to $34.45, Research) ended modestly lower following reports that it would cut base sticker prices for select 2006 models.

Computer software remained one of the best performing sectors on the day, with the Goldman Sachs Software (Charts) index adding 1.2 percent.

Among other movers, shares of Morgan Stanley (up $1.00 to $50.88, Research) rose 2 percent in active New York Stock Exchange trade on news that embattled CEO Philip Purcell will step down no later than March 2006.

The company -- which separately warned of a second-quarter earnings shortfall -- faced its latest hurdle Friday when a group of equity staffers departed for rival Wachovia Securities.

Biotech Connetics (down $5.64 to $15.13, Research) plunged 27 percent in unusually active Nasdaq trade after receiving a letter from U.S. regulators signaling that they would not approve its experimental acne treatment. The setback caused the company to cut its fiscal 2005 profit and revenue targets.

Shares of Northwest Airlines (down $0.75 to $5.58, Research) tumbled nearly 12 percent on reports that it may be heading for a Chapter 11 bankruptcy filing, according to an article in the Wall Street Journal.

Market breadth was positive and volume was moderate. On the New York Stock Exchange, advancers beat decliners nine to seven as 1.27 billion shares changed hands. On the Nasdaq, winners topped losers eight to seven on volume of 1.45 billion shares.

Treasury prices fell further, lifting the yield on the 10-year note to 4.09 percent from 4.04 percent late Friday. Treasury prices and yields move in opposite directions.

In currency trading, the dollar was little changed versus the euro and higher versus the yen.

COMEX gold rose $1.80 to $431.10 an ounce.