By Greg Stutchbury

WELLINGTON (Reuters) - Seven-times Tour de France winner Lance Armstrong is to compete in a triathlon event in New Zealand after he finishes his competitive cycling career at January's Tour Down Under in Australia, organizers have said.

Armstrong will compete at the Blue Lake Multisport Festival which is set for January 29-30 in Rotorua in New Zealand's famed geothermal region in the central North Island.

The 39-year-old American had hinted late last week that he would compete in the event after he posted the co-ordinates of it through his alter ego Juan Pelota's Twitter account.

Organizers checked the entries over the weekend and having discovered his name, contacted Armstrong's representatives.

"The rumors were not confirmed until this morning when organizers from the Rotorua Association of Triathletes (RATS) received an email from Armstrong's media advisor," organizer Charlotte Pearson said on their website (www.rats.org.nz) on Monday.

"This is a really big thing for RATS and for the event, especially since it is our 25th anniversary.

"The club were hoping to attract top New Zealand triathletes (such as)... Bevan Docherty, Kris Gemmell and Cameron Brown (who) all competed in the event when they were young.

"We were hoping for them to race again, we never dreamed that Lance Armstrong would be our headline athlete!"

Armstrong was a promising junior triathlete before switching full time to cycling.

The Blue Lake festival involves an aquathon (5.5km forest run/800m lake swim) and 2km open water swim on January 29 and a short-distance triathlon on January 30 comprising a 750m lake swim, 16km road cycle and 5.5km forest run.

Armstrong will compete on both days, Pearson said.

(Reporting by Greg Stutchbury; Editing by Ossian Shine)