UCI President Pat McQuaid refused to comment on the U.S. Anti-Doping Agency's report this week that accused Armstrong of systematic doping. 

Instead, McQuaid says inadequacies in the anti-doping system are failing to catch drug-using athletes. 

McQuaid says the UCI tests athletes repeatedly for doping but the federation can do little if the results are negative.

He says the anti-doping system has improved since the 1998-2009 period of Armstrong's career examined in the report.

The UCI has yet to decide whether to ratify USADA's decision to strip Armstrong of his seven Tour de France titles.

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