Speaking a week after the US Congress passed President Joe Biden's $1.2 trillion infrastructure investment package, she said "no single nation" could be relied upon to deal with these challenges alone.

She told President Emmanuel Macron and other leaders at the Paris Peace Forum conference that inequality gaps had narrowed and widened during human history but "throughout this pandemic the gaps have undoubtedly become larger".

"Globally, extreme poverty is on the rise -- as is extreme wealth," she said, adding "progress on gender equality is under threat" as is a child's right to an education.

"By virtually every measure, the gaps have grown. We face a dramatic rise in inequality and we must meet this moment."

"Why is it that one percent of the world now owns 45 percent of the world's wealth? Why is it that one in four people in our world lack access to clean drinking water at home?"

"We cannot be aware of these gaps and simply resign ourselves to them," said Harris, who is on a major multi-day visit to France aimed at easing tensions with Washington's oldest ally.

"We must agree that these growing gaps are unacceptable and we must agree to work together to address them," she added.

"The fact remains no single nation can take on inequality alone. A challenge this sizeable and seismic demands our world work together in solidarity."

Macron echoed her concerns in his remarks to the conference issuing a stark warning about the importance of demography, which was showing sharply different trends in the north and south of the globe.

"We cannot sustainably have a north which is getting more and more old in good health and a south which makes more and more children with so few perspectives," he said.

"This will only create tension unless we put demography -- and the inequalities that it creates -- at the heart of our policies of development and investment," said Macron.

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HARRIS