UPDATE 1-Bullard says Fed policy considerably easier in 2013

(Updates with more Bullard comments, background)

STARKVILLE, Miss., Feb 14 (Reuters) - The U.S. Federal Reserve has ramped up its monetary stimulus "considerably" this year compared to 2012 thanks to two significant changes, a senior Fed official said on Thursday.

St. Louis Fed Bank President James Bullard said the switch to outright open-ended bond purchases, plus the adoption of thresholds to guide expectations on when the Fed would start to raise interest rates, were making policy more effective.

"The current stance of U.S. monetary policy is considerably easier than it was in 2012," Bullard, a voting member of the Fed's policy-setting committee this year, told a forum at Mississippi State University.

The Fed replaced its program, called Operation Twist, of reinvesting the proceeds from the sale of shorter-dated securities into longer-dated bonds with outright bond buys, starting in January. Bullard said Twist had been relatively weak in terms of its policy punch.

In addition, the Fed has adopted thresholds to guide expectations on interest rates and has now committed to hold them near zero until unemployment reaches 6.5 percent, so long as inflation does not threaten to rise above 2.5 percent. The U.S. jobless rate in January was 7.9 percent.

Thresholds replaced a commitment to hold rates down until at least mid-2015, which economists complained could undermine the Fed's efforts to bolster confidence in a U.S. recovery.

"The date could be interpreted as a statement that the U.S. economy is likely to perform poorly until that time," he said. "I have called this an "unwarranted pessimistic signal."

As a result of dropping the date and shifting to outright bond buying, "2013 is characterized by a relatively potent open-ended outright asset purchase program combined with more effective threshold-based forward guidance," Bullard said.

Critics of the Fed's aggressive efforts to support a fragile U.S recovery warn these actions could spur future inflation.

Bullard said that so far these fears had been unwarranted, and argued that while the growth in the Fed's balance sheet might hinder a "graceful exit" when it starts to tighten policy, the lack of price pressures gave it room to maneuver.

"Current readings on inflation are rather low," Bullard said. "This may give the Committee some leeway to continue purchases longer than otherwise."

(Reporting By Alister Bull; Editing by Neil Stempleman)