LONDON — Athletes around the world will be subjected to out-of-competition tests for human growth hormone in the lead-up to the Beijing Olympics, marking a potential breakthrough against one of the most widely abused doping substances in sports.

David Howman, director general of the World Anti-Doping Agency, said today that newly produced HGH testing kits soon will be distributed to accredited doping labs around the globe to screen blood samples for the banned performance-enhancing hormone.

An improved HGH test also will be in place during the Aug. 8 to 24 Olympics.

"We are expecting that an athlete will see this is going to happen and will be deterred from using the substance," Howman said in a telephone interview. "There may be those who will take major risks. We hope that they are majorly caught out, simple as that."

A test for HGH was introduced at the 2004 Athens Olympics and also was used at the 2006 Winter Games in Turin. No positive tests for HGH were recorded at either games.

This will be the first time HGH testing is available on a widespread basis in the buildup to an Olympics. Surprise, out-of-competition testing is considered the most effective way of catching drug cheats.

"This is something that needs a huge push," Howman said. "HGH is a substance out there that has been used with impunity for many years. We think it's something we have to spend a lot of time on."

WADA reached a deal with a European company for large-scale production and distribution of the testing kits. Howman said the company, believed to be based in Germany, asked not to be identified.

The move came after a previous arrangement with a U.S. company fell through after it was taken over by another firm.

"This is groundbreaking because the situation had been impeding progress for a couple of years," Howman said.

Production of the kits has started and they will be available in a matter of weeks, he said, adding that they number "in the thousands, not tens of thousands."

Each testing kit can screen 10-20 blood samples, Howman said. In addition, blood samples can be frozen and tested years later for HGH.

Howman said he expects national and regional anti-doping bodies around the world to use the tests to target suspected drug cheats before the Beijing Games.

"The responsibility of ensuring the games are clean falls not only on the shoulders of the athletes but also on those who are selecting them, training them and medically guiding them," he said. "We would expect if an athlete decides to cheat, not only would the athlete be sanctioned, but so would the people around him."

The window for detecting HGH use has been limited to a period of 48 to 72 hours, giving athletes a chance to avoid detection by stopping in time for any traces to clear their system. Howman said the test has been "enhanced," but declined to elaborate.

"We're not telling athletes how long and how wide the window is at the moment," he said.

Howman said the HGH test has been validated both on a scientific level and on a legal basis to ensure it stands up against any court challenge.

"Both these steps have been taken and no longer provide any questions," he said.

At the Olympics, the drug-testing program will be run by the International Olympic Committee. The IOC says about 4,500 tests overall will be conducted during the Beijing Games.