The sweltering heat and humidity had the world track and field championships' competition committee contemplating moving up the time of the marathon.

But the committee met late Friday for more than two hours and decided to go ahead as scheduled with Saturday's race, which begins at 7 a.m. local time. The committee will add more water stations and extra medical staff.

The temperature reached 104 degrees last week and is expected to top 94 on Saturday, although weather forecasters are predicting scattered thunderstorms throughout the morning.

"We reviewed the weather forecasts and the weather for (Saturday) is deemed fine," said Paul Hardy, the events and competitions director for the international athletics federation. "It seems like it's going to cool down."

Morocco's Jaouad Gharib, a two-time defending champion in the marathon, has withdrawn from the competition citing an unspecified injury. His countryman, Abderrahim Goumri, is among the favorites, along with Qatar's Kenyan-born Mubarak Hassan Shami, who has the fastest time in the world in 2007 at 2 hours, 7.19 seconds.

The morning marathon begins the nine days of competition. The first day also includes opening ceremonies, the finals in the men's shot put and the women's 10,000-meter run, and the first two rounds of the much-anticipated men's 100 meters.

Jamaica's Asafa Powell and Tyson Gay of the U.S. start the process of becoming "The Man in Japan," as former sprinter Jon Drummond has dubbed the 100 race. The finals will be held Sunday night.

Powell enters the competition as the co-holder of the world record, but Gay has the fastest time in 2007 at 9.84 seconds. Powell shares the world record of 9.77 seconds with Justin Gatlin, who is not in Osaka to defend his title after testing positive for testosterone in April 2006.

Yasuhiro Uchiyama, a member of the Osaka world championships organizing committee, thinks the world mark could fall on Nagai Stadium's specially designed surface. It's a double-layered soft and hard rubber track that enhances traction.

"It's a very fast track. We hope a lot of world records can occur," Uchiyama said through an interpreter.

Uchiyama said he hasn't slept more than two hours a night over the last week. He's lost sleep making sure everything goes off without a problem.

"Everything will flow smoothly," Uchiyama said.

As for the intense weather expected during the world championships, Uchiyama just grinned.

"It's Osaka. It's hot and humid this time of year," he said. "We have a morning session that lasts until noon and an evening session that begins at 5 p.m. We don't have events under the most intense conditions of the day. We believe everything will be fine."

American decathlete Bryan Clay, the defending world champion from Hawai'i, won't be concerned about the weather. He'll simply think cool thoughts.

"It'll come down to your mental toughness and how much you want it," he said.

The decathlon is scheduled for Aug. 31 and Sept. 1.

American Reese Hoffa is a favorite in the shot put and has the top throw this season at 22.43 meters. Adam Nelson of the U.S. is the defending champion with his win in Helsinki in 2005.