By Yereth Rosen

ANCHORAGE, Alaska, March 13 (Reuters) - A Norwegian musher was poised on Tuesday to win the Iditarod Trail Sled Dog Race and notch the third victory ever for his home country in 46 years of the annual 1,000-mile (1609-km) trek across Alaska's wilderness.

Joar Leifseth Ulsom jumped into first place of the world's most famous sled-dog race on Monday when he passed French native Nicolas Petit on the Bering Sea ice. Petit, who had held a comfortable lead, went astray as he ventured into blowing snow and lost the trail, forcing him to backtrack.

Petit told the Anchorage Daily News that he was led off-course by some markers left over from the Iron Dog snowmobile race.

By midday on Tuesday, Ulsom and Petit and their dogs had paused in the Inupiat Eskimo village of White Mountain, a mandatory eight-hour rest stop before the final dash to the finish line in Nome, a coastal Gold Rush town 77 miles (124 km)to the west.

Ulsom, who arrived 3-1/2 hours ahead of Petit, was expected to return to the trail in the afternoon and arrive at the finish line sometime after midnight, capping nine days of competition.

If he prevails, Ulsom will become the second Norwegian to win the 1,000-mile Iditarod. Countryman Robert Sorlie won twice before - in 2003 and again in 2005.

From the Norwegian town of Mo i Rana, just south of the Arctic Circle, the 31-year-old Ulsom has built an impressive international mushing record.

He has finished in the top seven in all seven of his past Iditarod races, and was the fastest-ever rookie in 2013. He is a two-time winner of the long-distance Nadezhda Hope race in Russia's Chukotka region, and won a 2012 sprint championship in Chukotka.

Petit also brings some international flair to the Iditarod. The 36-year-old contestant grew up in France's Normandy region and moved to Alaska in 1992. He lives in the ski town of Girdwood.

Sixty-seven mushers and their dogs started the Iditarod in Anchorage on March 3. As of Tuesday afternoon, six had dropped out of contention. Most Iditarod mushers are from Alaska, but each year there are several Norwegians in the race.

The Iditarod finishers will split a total $500,000 prize purse, and the first-place champion also gets a new pickup truck.

As Ulsom and Petit waited out their last Iditarod rest, four-time Iditarod champion Dallas Seavey was in Norway, where he was leading in the 1,100-kilometer (682-mile) Finnmarksløpet.

Seavey, at the center of a dog-doping scandal, withdrew from this year's Iditarod. Four of his dogs tested positive for a banned opioid after last year's race, but he has proclaimed his innocence and has accused Iditarod managers of botching his case. He has also suggested that he was the victim of sabotage. (Editing by Steve Gorman and Sandra Maler)