LAUSANNE, Switzerland (AP) — Seeking to avoid "negative surprises" about past doping by Russian athletes after they compete at the Pyeongchang Olympics, IOC President Thomas Bach explained Wednesday why invitation rules must be strict.

Bach told reporters in a conference call that only clean athletes with "not the slightest doubt or suspicion" about them should go to the games that open Feb. 9. It is the first Winter Games since the doping-tainted Sochi Olympics in 2014.

"The final invited list will consist of clean athletes, so that neither Russia nor the Olympic movement will have to face any negative surprises," the International Olympic Committee leader said.

Six-time short-track speedskating gold medalist Viktor Ahn is among several high-profile Russians blocked from competing in South Korea by an IOC panel that is assessing each athlete's testing history and potential forensic evidence.

Five hockey players have also been barred, including former NHL players Sergei Plotnikov, Valeri Nichushkin and Anton Belov.

The IOC has not confirmed any names before publishing a list of invited athletes this weekend, nor has it detailed all the criteria being used by the panel to vet each athlete.

"There could be a suspicion, there may be even ongoing procedures, there could be many factors which did not lead to the satisfaction of the panel," Bach said.

Declining to discuss individual cases, he did suggest potential evidence from a Moscow testing laboratory's database is one such factor.

The database trove being studied by the IOC invitation panel covers years of the lab's work when Russia operated a state-backed program of doping and cover-ups across summer and winter sports.

"This is why we had the (World Anti-Doping Agency) chief investigator Mr. (Gunter) Younger in this group to contribute with his first-hand experience," Bach said.

Another possible reason for excluding a Russian athlete from the Olympics is appearing on the so-called "Duchess List" of athletes using a steroids cocktail compiled by former lab director Grigory Rodchenkov. He is a key whistleblower now living as a protected witness in the United States.

Bach said that forensic evidence from tampered urine samples — "salt analysis, DNA inconsistencies" — and suspect readings from an athlete's biological passport could also lead to exclusion from the invited Russian team.

Organizers want to avoid situations "where there are new facts arriving," said Bach, who wants to avoid altering Pyeongchang results and reallocating medals to clean athletes after the games.

"It is extremely important and this is one of the reasons why we have the widest and the strictest ever pre-games testing program," he said.

Russian athletes that are invited will compete as "Olympic Athletes from Russia" under the Olympic flag, and in neutral uniform.