The S&P 500 hit a 29-month high on Wednesday as investors snapped up commodity and tech shares ahead of the Federal Reserve's statement, expected to continue to be supportive of markets.

U.S. President Barack Obama's call on Tuesday for a lower corporate tax rate also supported equities, as any move in that direction is seen as a boost to profits.

Pretty good earnings from a few tech names are certainly helping today, said Michael James, senior trader at Wedbush Morgan in Los Angeles, citing reports from Juniper Networks Inc and Fortinet Inc .

There is some positive spillover from the president's speech last night and people are feeling better about the tape, doing a good job of shrugging off Boeing, James said.

Boeing Co fell 3 percent to $70.06 after the U.S. plane maker and Dow component posted a drop in quarterly profit and offered a disappointing forecast.

Commodity shares got a boost after Allegheny Technologies Inc forecast stronger sales in 2011, helped by higher base prices for metals and a stronger aerospace and defense market. Allegheny rose 8 percent to $63.08, leading the S&P materials sector index <.GSPM> up 1.7 percent.

The Dow Jones industrial average <.DJI> gained 24.07 points, or 0.20 percent, to 12,001.26. The Standard & Poor's 500 <.SPX> rose 6.18 points, or 0.48 percent, to 1,297.36. The Nasdaq Composite <.IXIC> added 20.16 points, or 0.74 percent, to 2,739.41.

The Dow traded above 12,000 for the first time since June 2008.

Investors awaited comments from the U.S. Federal Reserve, which is expected to nod to an improving economic outlook as it reaffirms a plan to buy government debt to help speed the recovery. A Fed statement following a two-day meeting, its first of the year, is expected at about 2:15 p.m. EST (1915 GMT).

The S&P 500 index continues to show overbought readings in various short-term technical indicators after last week's decline released some selling pressure.

Short-term support kicks in at 1,284, its 14-day moving average, while the 1,300-1,305 area, closing highs reached in August 2008, could result in resistance.

Network equipment maker Juniper Networks Inc's quarterly sales beat Wall Street's expectations and its shares climbed 6 percent to $36.91, while Fortinet shares jumped 14.1 percent to $38.69 a day after the network security systems provider reported market-beating quarterly results.

Thomson Reuters' latest data showed 69 percent of the 144 S&P 500 companies that have reported earnings so far have beat estimates.

In the latest economic data, new U.S. single-family home sales rose in December to their highest level in eight months. The PHLX housing index <.HGX> advanced 0.9 percent, with Hovnanian Enterprises Inc adding 5.2 percent to $4.69.

(Reporting by Rodrigo Campos; Editing by Jan Paschal)