NEW YORK (Reuters) - The National Hockey League formally approved the sale and relocation of the Atlanta Thrashers to Winnipeg Tuesday, rubber-stamping the first franchise relocation in the league since 1997.

Winnipeg hockey fans began celebrating last month when the Thrashers were sold to True North Sports and Entertainment, led by partners Mark Chipman and billionaire David Thomson, Canada's richest man and chairman of news and information company Thomson Reuters.

But the sale agreement was dependent upon the approval of the NHL's board of governors, who met in Manhattan Tuesday to cast their votes.

"The Board unanimously approved both the sale of the Atlanta franchise to True North, which is Mark Chipman and David Thomson, and the relocation of Thrashers to Winnipeg," NHL Commissioner Gary Bettman said.

The Winnipeg franchise has still not been named but marked Tuesday's announcement by launching its own website. The team will initially play in the Southeast division in 2011-12, but was expected to be moved to the Western Conference from the following season.

"We are very honored by the NHL Board of Governors' unanimous decision today," Chipman said in a statement on the team's website (winnipeg.nhl.com)."

"We know that the fans of this province have an appetite for NHL hockey that is rivaled by few in the league and intend to work very hard to make Manitobans proud of our franchise for years to come."

(Reporting by Julian Linden; Editing by Rex Gowar)