The tender offer is scheduled to expire on March 14. The company said it will accept a portion of its 2016 notes that are validly tendered and not withdrawn before 5 p.m. EDT on Feb. 28.

The company has a total of $1.5 billion of the notes outstanding.

Viacom has retained BofA Merrill Lynch, Mitsubishi UFJ Securities, Morgan Stanley, and Wells Fargo Securities to serve as dealer managers in the tender offer.

Class A shares of Viacom slid 27 cents to $51.27 in late morning trading.

Traders are monitoring the situation in Cairo as protesters and regime supporters skirmished for a second day at a central Cairo square while new lawlessness spread around the city. New looting and arson erupted, and gangs of thugs supporting President Hosni Mubarak attacked reporters, foreigners and rights workers while the army rounded up foreign journalists.

Though the market impact of Egypt's turmoil has diminished as the week progressed, it continues to fuel uncertainty.

"Fresh turmoil in Egypt and risk of contagion will unsettle equity markets and maintain upward pressure on oil price," said Neil MacKinnon, global macro strategist at VTB Capital.

In Europe, the FTSE 100 index of leading British shares closed down 0.3 percent at 5,983.34 while Germany's DAX rose 0.1 percent to 7,193.68. The CAC-40 underperformed its peers, ending 0.7 percent lower at 4,036.59.

BlackRock, the world's biggest money management company, says it holds nearly 7 percent of the Class B stock of Warren Buffett's company.

BlackRock revealed Wednesday that it owns 68.4 million Class B shares of Berkshire Hathaway Inc. The New York-based money manager said in a filing with the Securities and Exchange Commission that it held the shares at the end of 2010.

The stake will likely give BlackRock's investors little say in Berkshire because each of the company's Class B shares carries one-ten-thousandth of the voting rights of a Class A share.

Omaha-based Berkshire owns roughly 80 subsidiaries, including insurance, clothing, utility, furniture, jewelry and corporate jet firms. It also has major investments in such companies as Coca-Cola Co., Washington Post Co. and Wells Fargo & Co.

Another big stock market index, the Standard & Poor's 500, reached a milestone of its own Tuesday. It closed above 1,300.

Investors found plenty of reasons to send stocks sharply higher. Earnings reports from companies including Pfizer, UPS and Archer Daniels Midland were better than expected. And manufacturing had another good month in January.

According to preliminary calculations, the Dow, which fell to a low of 6,547 in March 2009, soared 148 points, or 1.3 percent, Tuesday to 12,040.16.

The S&P 500 rose 21, or 1.7 percent, to 1,307.59, its first close above 1,300 since August 2008.

The Nasdaq rose 51, or 1.9 percent, to 2,751.19

Volume on the New York Stock Exchange came to 1.1 billion shares. Five stocks rose for every one that fell.

The exchange in Caracas began operating with corporate bonds issued by the Venezuela-based subsidiary of Japanese carmaker Toyota and the local company Envases Venezolanos, Planning and Finance Minister Jorge Giordani said on state television as he visited the bourse for its official launch.

He did not provide details about the corporate bonds such as amounts or interest rates, nor how much activity there was on Monday.

The Bicentennial Public Securities Exchange will compete with the privately run Caracas Stock Exchange.

Trading in the private stock exchange has dwindled after President Hugo Chavez nationalized some companies that traded shares, and it has been nearly paralyzed since securities regulators shut down and took over management of 47 brokerage companies last year.