Stocks rose for a sixth day on Wednesday as investors anticipated that the U.S. Federal Reserve will announce a fresh stimulus plan to support the economy at the end of a two-day monetary policy meeting.

The Fed is expected to announce a new round of bond buying later on Wednesday to boost a fragile economic recovery threatened by political wrangling over the government's budget. The monetary policy committee's decision is expected around 12:30 p.m. ET.

The S&P 500 was up for a sixth day, its longest winning streak since August, although gains have been less than 0.5 percent per day, on average.

"The market is waiting on the Fed, anticipating the open check to be out again, but we will see. Anything less than enormous will be disappointing to the market," said Joe Saluzzi, co-founder of New Jersey-based brokerage Themis Trading LLC.

The Dow Jones industrial average was up 35.56 points, or 0.27 percent, at 13,284.00. The Standard & Poor's 500 Index was up 4.04 points, or 0.28 percent, at 1,431.88. The Nasdaq Composite Index was up 4.31 points, or 0.14 percent, at 3,026.62.

With just two weeks of trading left this year, the S&P 500 is up about 14 percent so far; it ended the year flat in 2011.

BlackRock, one of the world's biggest asset managers, expects the S&P 500, the broad measure of U.S. stocks, to scale new heights in 2013 and reach 1,600 by the end of the year. That's a gain of more than 12 percent from current levels and would surpass the index's previous peak of 1,576.09 set in 2007.

Negotiations intensified to avert the "fiscal cliff" - tax hikes and spending cuts that kick in early in 2013 - ahead of a year-end deadline as President Barack Obama and U.S. House of Representatives Speaker John Boehner spoke by phone on Tuesday after exchanging new proposals.

3M Co pointed to a profit rise of about 8 percent next year as the U.S. economy continues its slow recovery. The stock was down 0.5 percent at $93.23 in early trading.

Costco Wholesale Corp posted a 30 percent rise in quarterly profit, beating expectations, as the largest U.S. warehouse club chain saw sales rise and got a lift from higher membership fees. [ID:nL5E8NC3WN] But the stock fell 0.7 percent to $97.53 in early trading Wednesday, after having gained more than 1 percent in premarket trading.

(Editing by Bernadette Baum)