UPDATE 1-Fed will start buying Treasuries on Wednesday

(Adds analyst quote, background on Treasury purchases)

By Kristina Cooke and Chris Reese

NEW YORK, March 24 (Reuters) - The U.S. Federal Reserve will start buying Treasury bonds on Wednesday, the New York Fed said on Tuesday, beginning the most decisive escalation of its efforts to help end a deepening recession.

The Fed surprised markets at its policy-setting meeting last week when it announced it would buy up to $300 billion of Treasury securities over the next six months. It will be the first time the Fed has bought longer-dated U.S. government debt since the 1960s.

Treasuries cut their losses after the Fed detailed its buying plans.

"It was a big deal because it is happening so fast," said William Larkin, fixed-income portfolio manager at Cabot Money Management in Salem, Massachusetts. "It tells you that (the Fed) is serious -- they are operating on all cylinders, which is a positive."

Wednesday's purchases will target the February 2016-to-February 2019 maturity range. Aside from Wednesday's purchase, the New York Fed also announced four more operations, on March 27, March 30, April 1 and April 2.

The most dramatic Treasury market move was in U.S. 30-year bonds, as the March 30 purchases would target the 2026-to-2039 maturity range.

U.S. long bonds dramatically reversed losses to rise nearly two points in price after the announcement, with the yield plunging to 3.59 percent from 3.76 percent before the announcement.

"It takes away from fears of rising interest rates, and the 30-year really popped up in price," Larkin said.

The New York Fed said last week that it was focusing on the two- to 10-year maturity range, dampening market hopes that it would buy 30-year bonds.

Starting April 1 and continuing every two weeks, the New York Fed will issue a tentative schedule for its purchases, including the maturity sector or sectors to be targeted.

(For a tentative schedule of the operations, please see www.newyorkfed.org) (Reporting by Kristina Cooke and Chris Reese; Editing by Jonathan Oatis)