Two members of a panel set up to appraise the World Health Organization's handling of the H1N1 pandemic have stepped down because they were involved in the response the review committee is assessing.

A statement released by the Geneva-based agency suggested they felt that involvement could be seen as a conflict, given that the review is meant to be an independent evaluation.

The review committee chair said Tuesday the men — Australian virologist John MacKenzie and Dr. Tony Evans, head of aviation medicine at the International Civil Aviation Organization — will make themselves available to the panel as expert witnesses if and when needed.

"Both have been closely engaged in deliberations at WHO which our committee is charged to review," said Dr. Harvey Fineberg, who is also president of the U.S. Institute of Medicine.

"They each concluded it would be better to avoid the position as reviewer of their own earlier actions."

MacKenzie is also chair of the so-called Emergency Committee of experts that has been advising WHO Director General Margaret Chan on the pandemic.

The identities of other members of that committee have not been made public, a fact that has fuelled criticism of the WHO's handling of the outbreak. Chan has said those names are being kept secret to protect members from external pressure. She has promised to make their names known once the pandemic is declared over.

MacKenzie also played a pivotal role in the WHO's response to SARS. He headed a scientific committee struck to piece together, in real time, key information about the new disease.

The review panel will present a final report next year.

With files from The Associated Press