Speaking about her new role to Newstalk ZB's Mike Yardley this morning, Clark said the inquiry would focus on how effective the response which the WHO has co-ordinated has been.
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She said there would be other parallel inquiries going on within the WHO as well.
"We'll have to write detailed terms of reference to see how we move forward with this."
The way member countries of the WHO have handled the situation would also be looked at carefully, she said.
Clark acknowledged that the move to ban travel from China had worked for New Zealand - but not for other countries.
"One of the issues may be going forward is does the WHO...need more powers?"
Asked whether she hesitated about taking up the co-chair job, she said: "Yes - because it's mission impossible."
She said it was hard to say whether New Zealand's success with battling Covid-19 had anything to do with her appointment.
Clark acknowledged that her co-chair teammate, former Liberia president Ellen Johnson Sirleaf, was most likely called upon due to her experience with the Ebola outbreak during her reign about six years ago.
'Covid-19 has left no country untouched'
WHO director-general Tedros Adhanom Ghebreyesus acknowledged the magnitude of the situation the world has found itself in - and the respective response that was therefore needed.
He called Covid-19 a "once-in-a-century" pandemic that had hammered home a critical lesson - "when it comes to health, our destinies are intertwined".
"The Covid-19 pandemic has left no country untouched. It has humbled all of us.
"It is often said that disease knows no borders. It does not care about our political differences and it disregards the distinctions we draw between health and economy, lives and livelihoods."
Ghebreyesus said Clark would work alongside Sirleaf.
"I cannot imagine two more strong-minded, independent leaders to help guide us through this critical learning process to help us understand what happened.
"An honest assessment and to help us understand also what we should do to prevent such a tragedy in the future, to collectively - as a world - say 'never again' to such a tragedy."
He said the WHO would be an "open book" to Clark's review and he expected all WHO member states to also be transparent.
Clark honoured to co-chair panel
Clark posted a message on her official Twitter page after the news broke.
"Honoured to be announced by (Dr Ghebreyesus) as a co-chair of Independent Panel for Pandemic Preparedness and Response with former Liberia President (Sirleaf).
"Aim to provide evidence-based path for future."
The panel will report back to health ministers in November.
Clark says the assignment can only be described as exceptionally challenging.