* QE3 gets muted response after weeks of anticipation
* Buy the rumor, hold on the fact as oil, copper a little higher
* Gold highest since February; oil faces from 4-1/2 month high
NEW YORK, Sept 13 Major commodity markets, including oil and copper, gave an initial tepid response to the Federal Reserve's third effort to revive the U.S. economy, leaving gold the biggest beneficiary of a plan that has been slowly baked into markets for weeks.
Prices jumped immediately on Thursday after the Fed said it had agreed to buy $40 billion of mortgage debt per month and continue to purchase assets until the outlook for jobs improves substantially, meeting broad expectations for a third set of quantitative easing to get growth back on track.
But an hour after the news hit, gold had extended gains to more than 2 percent or $35, reaching its highest since February at $1,765 an ounce, while oil and copper prices were only a bit firmer, having first lurched higher and then lower. November Brent crude was up 47 cents at $115.80 a barrel.
As the dust settled and traders awaited Chairman Ben Bernanke's press conference at 2:15 p.m. EDT (1815 GMT), a consensus emerged that the Fed plan offered no reason for despair, but likewise little cause for hope of an abrupt economic turn-around that might boost demand for raw materials.
"The Fed has taken the middle road with a modest, defined contribution purchase program and extended rate guidance," said Joseph Trevisani, chief market strategist at Worldwide Markets in Woodcliff Lake, New Jersey.
In a plan that offered relatively few surprises, meeting expectations for more bond buying and an extension of the Fed's ultra-low interest rate pledge to mid-2015, the most significant shift was the committee's decision to tie the duration of its bond binge to economic conditions, rather than a finite sum.
U.S. stock markets pushed higher as the news settled in, rising 1 percent. The U.S. dollar index fell 0.35 percent.