The world is "at war" against Covid-19, the UN chief said Monday, calling for the application of wartime logic to the inequitable access to the weapons needed to fight the pandemic.

United Nations Secretary-General Antonio Guterres decried the "tsunami of suffering" sparked by the coronavirus crisis.

Addressing the opening of the World Health Organization's main annual assembly of member states, he pointed out that more than 3.4 million people have died and some 500 million jobs had disappeared since the disease first surfaced in China in late 2019.

"The most vulnerable are suffering most, and I fear this is far from over," Guterres said, stressing the ongoing dangers of "a two-speed global response."

"Sadly, unless we act now, we face a situation in which rich countries vaccinate the majority of their people and open their economies, while the virus continues to cause deep suffering by circling and mutating in the poorest countries," he said.

"Further spikes and surges could claim hundreds of thousands of lives, and slow the global economic recovery," he said, insisting that "Covid-19 cannot be beaten one country at a time."

Faced with this dire situation, Guterres urged recognition of the fact that "we are at war with a virus."

"We need the logic and urgency of a war economy, to boost the capacity of our weapons," he said.

The UN chief last week called on the G20 to set up a task force that brings together all countries with vaccine production capacities and others who can help boost manufacturing of vaccines and other tools needed to battle Covid.

"It should aim to at least double manufacturing capacity by exploring all options, from voluntary licenses and technology transfers to patent pooling and flexibility on intellectual property rights," he said.

The task force should also address equitable global distribution of vaccines, treatments and diagnostics.

The WHO and others have created Covax, a global vaccine-sharing programme, but it remains severely underfunded and has faced significant supply shortages, delaying efforts to roll out jabs in poorer countries.

To date, only 0.3 percent of Covid vaccine doses have been administered in the world's poorest countries, which are home to nearly 10 percent of the global population.

In addition to battling Covid-19, Guterres stressed the importance of preparing for the next pandemic, backing a range of recommendations put before the assembly for reform and strengthening of the WHO and of the global health system.

"The world needs political commitment at the highest level to transform the existing system," he said.

"The WHO must be at the heart of global pandemic preparedness. It needs sustainable and predictable resources, and it must be fully empowered to do the job demanded of it."

Guterres urged member states to decide a way forward to "take the bold decisions necessary to end this pandemic."

"Covid-19 must be a turning point."