NEW YORK — Stocks turned mixed in early trading today as investors lost some of their initial enthusiasm over the government's plans to shore up confidence in mortgage financiers Fannie Mae and Freddie Mac.

Shares of the government-chartered companies advanced in volatile trading after tumbling last week amid concerns they would succumb to losses in their mortgage portfolios. Statements Sunday from the Treasury and the Federal Reserve that they would aid the companies if needed has eased some worries of further turmoil in the credit markets.

The Fed said it would lend to the two companies "should such lending prove necessary." Treasury Secretary Henry Paulson said his department is asking Congress for quick approval of a plan to expand its line of credit to the two companies and to make an equity investment in them if necessary.

Wall Street has been on edge about the well-being of the companies because Fannie Mae and Freddie Mac hold or back $5.3 trillion of mortgage debt, about half the outstanding mortgages in the United States. Worries over their future led to a volatile session Friday in which the Dow Jones industrial average dipped below the 11,000 mark for the first time in about two years before paring its losses.

While the companies say they have adequate access to capital, the government's effort to help the companies is designed to reassure investors who have grown nervous about further fallout from the nearly year-old credit crisis. A weak housing market has eroded the value of many securities backed by now faltering mortgages.

In the first hour of trading, the Dow rose 27.60, or 0.25 percent, to 11,128.14 after spiking nearly 140 points in the opening minutes of trading.

Broader stock indicators were mixed. The Standard & Poor's 500 index rose 1.74, or 0.14 percent, to 1,241.23, and the Nasdaq composite index fell 6.68, or 0.30 percent, to 2,232.40.

Declining issues outnumbered advancers by about 4 to 3 on the New York Stock Exchange, where volume came to 191.1 million shares.

Bond prices rose. The yield on the benchmark 10-year Treasury note, which moves opposite its yield, fell to 3.93 percent from 3.96 percent late Friday.

The dollar was mixed against other major currencies, while gold prices rose.

Light, sweet crude fell 53 cents to $144.55 on the New York Mercantile Exchange.

Fannie Mae shares rose 24 cents, or 2.3 percent, to $10.49, while Freddie Mac jumped 29 cents, or 3.7 percent, to $8.04 after announcement of the government's plans.

Sen. Charles Schumer on Sunday defended himself against claims by regulators that he was in part to blame for a run on IndyMac Bancorp Inc. that led to the bank's takeover by the government Friday. IndyMac is the largest regulated thrift to fail and the second largest financial institution to close in U.S. history, regulators said after taking control of the bank.

Anheuser-Busch Cos. agreed to a sweetened $52 billion takeover bid from Belgian brewer InBev SA. The deal involving a marquee name in American business combines the maker of Budweiser and Bud Light with the producer of Stella Artois and Beck's. Anheuser-Busch rose 87 cents to $67.37.

Yahoo Inc. revealed Saturday it had rejected Microsoft Corp.'s latest attempt to acquire its online search engine in a joint proposal made with activist investor Carl Icahn, who is leading an effort to remove Yahoo's current board. Yahoo fell 78 cents, or 3.3 percent, to $22.79, while Microsoft rose 42 cents to $25.67.

The renewed concerns about the financial sector come in what is expected to be a busy week for corporate news, with a flurry of quarterly results due from names like Intel Corp., Cola-Cola Corp., Microsoft Corp. and Citigroup Inc.

The Russell 2000 index of smaller companies fell 1.62, or 0.24 percent, to 673.33.

Overseas, Japan's Nikkei stock average rose 0.45 percent. In afternoon trading, Britain's FTSE 100 rose 1.95 percent, Germany's DAX index rose 1.55 percent, and France's CAC-40 advanced 1.93 percent.