ST. LOUIS (AP) _ Steve Fossett's attempt to circle the globe in a balloon has entered a critical period, as weather and fatigue prove to be tough adversaries.

``We really don't know at this point where the balloon wants to go,'' said Bob Rice, meteorologist for Fossett's mission control at Washington University in St. Louis.

``At the moment, we're sort of in a rest area, waiting for the freeway to open again,'' Rice said Thursday.

The Chicago millionaire, making his fourth attempt to fly around the globe, was approaching the halfway point of his journey. But he was in danger of being drawn into a high-pressure system over the Indian Ocean that ``would make him loop and go nowhere,'' said Alan Blount, control center director.

Thursday afternoon, however, trackers saw a tendency for the balloon to turn right, which would indicate Fossett had found a layer of winds that would get him out of danger and put him on a path toward Australia.

Fossett, 54, is not in voice contact with his ground crew. They communicate via e-mail.

By late evening, Fossett was at 23,000 feet and about 2,700 miles northwest of Perth, Australia. He had traveled more than 9,600 miles from the starting point on Aug. 7 in Mendoza, Argentina.

``Right now the balloon is well-positioned,'' Rice said.

Fossett's messages on Thursday indicated that his spirits were down from spending hours making the navigational adjustments, Rice said. But the adventurer was able to get some much-needed sleep and was working with the control team today get the Solo Spirit back on course.