That's according to internal documents seen by Reuters.

They show the wh ose global scheme to deliver the vaccines faces a very high risk of failure, potentially leaving nations home to billions of people vulnerable to the virus.

The World Health Organization's Kovacs program is the main global scheme to vaccinate people in poor and middle income countries around the world.

It aims to deliver at least two billion vaccine doses by the end of 2021 to cover 20% of the most vulnerable people in 91 countries, mostly in Africa, Asia and Latin America.

But internal documents show the scheme's promoters say the program is struggling from a lack of funds supply risks on complex contractual arrangements.

All of the's could make it impossible to achieve their goals, the report says.

The risk of failure is higher because the scheme was set up so quickly operating in quote uncharted territory.

The W.