Stocks fluctuated Thursday as worries about the financial sector offset enthusiasm over better-than-expected sales from discounters and an agreement for Dow Chemical Co. to acquire rival Rohm and Haas Co.

Mortgage finance companies Fannie Mae and Freddie Mac fell sharply because of continued concerns about their access to financing. Shares in the two government-chartered companies have struggled of late on worries that they will be forced to sell more new shares than anticipated to compensate for losses from the housing slump.

Fannie shares fell more than 16 percent and Freddie shares dropped nearly 30 percent. Investment banks were also weak; Lehman Brothers Holdings Inc. fell $2.82, or 14.3 percent, to $16.92.

The declines in financials came after Treasury Secretary Henry Paulson told Congress that the market can’t expect the government to bail out troubled financial companies.

“For market discipline to effectively constrain risk, financial institution must be allowed to fail,” he said.

In midmorning trading, the Dow Jones industrial average fell 34.44, or 0.31 percent, to 11,113.00.

Broader stock indicators were mixed. The Standard & Poor’s 500 index fell 5.96, or 0.48 percent, to 1,238.73, while the Nasdaq composite index rose 1.92, or 0.09 percent, to 2,236.81.

Meanwhile, the Organization of Petroleum Exporting Countries said Thursday world energy needs will spike by more than 50 percent by 2030. But, it said adequate oil reserves, conservation and new methods of recovery mean supply will keep pace with demand. Oil rose $1.65 to $137.70 a barrel.

But not all news was downcast. Among discounters, Wal-Mart Stores Inc. said it got a boost from the government’s stimulus package, and it raised its forecast for the current quarter. Meanwhile, Dow Chemical said it would acquire specialty chemicals maker Rohm and Haas in a $15.29 billion all-cash deal.

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