ELIM, Alaska (AP) _ Susan Butcher, bundled against biting winds and subzero temperatures, widened her lead and seemed assured of an unprecedented third straight victory in the 1,150-mile Iditarod Trail Sled Dog Race.

Butcher, who left this checkpoint just as her closest competitor arrived Tuesday, was expected to cross the finish line in Nome today.

If Butcher wins, it will be the fourth consecutive year that a woman has won the 16-year-old race. Libby Riddles of Teller won in 1985, and Butcher won in 1986 and 1987, setting a course record each year.

Butcher left Elim, 123 miles from Nome, at 5:11 p.m. Tuesday, after stopping in the Eskimo village for two hours to feed and rest her dog team. Martin Buser of Big Lake arrived two minutes before she left.

Butcher, a resident of Manley, took the lead early Tuesday and has not yielded it. She left Elim with 10 of the 17 dogs she started with March 5 in Anchorage; the others were dropped at checkpoints along the trail.

Buser was traveling with 12 of his original 20 dogs still in harness.

Subzero temperatures and biting winds continued to hinder the leaders, and weather forecasters said the wind chill factor could sink to minus 70 degrees along the trail's final miles.

In each of her two previous victories, Butcher proved the strength and endurance of her team in the final, windswept miles along the barren Bering Sea coast. Her elapsed time last year was 11 days, 2 hours.

Her closest rival last year was four-time Iditarod champion Rick Swenson of Two Rivers, who ran neck-and-neck with Butcher until his dogs refused to continue just 22 miles from the finish.

This year, Swenson was about six hours behind Butcher at last report, leaving Koyuk at 2 p.m. Tuesday in third place. Running in fourth was Joe Garnie of Teller.

Herbie Nayokpuk of Shishmaref was fifth. Seventy-year-old Joe Redington of Knik, who took an early lead and held it for more than 400 miles, was sixth.

Redington, known as the ''Father of the Iditarod'' for organizing the first race in 1973, has run all but two races and placed as high as fifth, but has yet to win.

The first musher to Nome collects $30,000 of a $150,000 purse; the next 19 finishers split the rest. Five of the 52 teams that started the race have dropped out.