The head of the World Anti-Doping Agency defended the doping tests that embroiled Marion Jones and Floyd Landis in high-profile cases, saying ``in the long run, the system works.''

WADA chairman Dick Pound said Thursday he has full confidence in EPO tests, which produced an initial positive finding for Jones but came back negative in the backup sample, as well as the testosterone tests that ensnared Tour de France winner Landis.

WADA has asked the Los Angeles laboratory that analyzed Jones' samples to provide the agency with all the documents in the case to determine if there were any mistakes. The issue most likely will be discussed by WADA's executive committee in Montreal this weekend.

``It's standard procedure when samples don't match,'' Pound said during a conference call. ``We're confident about the test, no question about that.''

Jones, a three-time Olympic gold medallist, tested positive for the blood-boosting hormone EPO on June 23 at the U.S. championships in Indianapolis, where she won the 100 metres. But she was exonerated when the second sample failed to confirm the ``A'' result, a highly unusual occurrence.

``We're interested in any case when the A and B don't match, both from the perspective of trying to improve the test if there was a technical glitch and understanding how the differences arose,'' Pound said.

The Montreal lawyer said it was appropriate Jones was exonerated of any doping violation because of the conflicting samples.

``We'd rather let some who may be guilty go free than sanction somebody who shouldn't be sanctioned,'' he said.

Pound cited a court ruling in Germany this week upholding the legitimacy of the EPO test in the case of middle-distance runner Bernard Lagat. The Kenyan-born Lagat, who now competes for the United States, tested positive for EPO in 2003 but was cleared when the B test was negative. Pound said Lagat failed in a bid for damages in a German court, contending the test was flawed.

``We take some comfort in that outcome,'' he said.

The WADA chief also defended the tests administered to Landis, who was cited for elevated testosterone and synthetic testosterone during the Tour de France and faces being stripped of his title.

Landis' attorney is questioning the accuracy of the testosterone tests, handled by the WADA-accredited lab in France, and asking that the doping charges be dismissed.

Without addressing the specifics, Pound said he was confident the U.S. Anti-Doping Agency, which is dealing with the Landis case, would not accept any flawed defence.

``Just because someone is making excuses does not mean a responsible anti-doping agency is going to roll over and play dead,'' he said.

Pound said there was no reason to question the credibility of the French lab.

Cycling's governing body has been ``quite vociferous in support of the lab,'' Pound said. ``If they found something I'm satisfied it was there. I haven't seen all the evidence, and we'll sit and wait to see what USADA and UCI do about it.''

Pound said doping labs, which do not comment publicly on ongoing cases, should be free to defend themselves against allegations of botched testing.

``It would be useful for ... people who see these statements, some of which are irresponsible, to take issue with them,'' he said. ``But, in the long run, the system works.''

Pound spoke ahead of WADA's executive committee meeting Saturday. The agency will consider banning the use of hypoxic or hyperbaric tents and chambers, which are used by many athletes to replicate high-altitude conditions and boost their level of oxygen-rich red blood cells.

WADA's ethics and education committee has ruled that the chambers enhance performance and violate ``the spirit of sport.''

``The moral question is simple,'' Pound said. ``It is one thing if you are prepared to go physically endure the rigours of training at altitude. But to be at sea level and climb into a tent and go to sleep pretending you're at altitude, and getting the same result, is artificial.''

A final decision will be up to the 12-member executive body.

``It's an issue that probably attracts more heat than light in the discussions,'' Pound said. ``There are entrenched positions on both sides. We'll have to wait and see.''

WADA also will approve the banned substances list for 2007, review the terms of the World Anti-Doping Code and urge national governments to speed ratification of the UNESCO convention on doping. Only 17 countries have ratified the treaty so far; at least 30 are required for adoption.