UNITED NATIONS - UN Secretary-General Antonio Guterres on Friday asked the world to declare war on COVID-19, two days after the World Health Organization (WHO) characterized the situation as a pandemic.

"We must declare war on this virus," said Guterres in a video message.

"That means countries have a responsibility to gear up, step up and scale up -- by implementing effective containment strategies, by activating and enhancing emergency response systems, by dramatically increasing testing capacity and care for patients, by readying hospitals ... and by developing life-saving medical interventions," he said.

All people have a responsibility to follow medical advice and take simple and practical steps recommended by health authorities, he said.

Guterres warned that the world is facing an unprecedented health threat.

As the virus is spreading and the danger is growing, health systems, economies, and day-to-day lives are being severely tested. The most vulnerable are the most affected, particularly the elderly and those with pre-existing medical conditions, those without access to reliable health care, and those in poverty or living on the edge.

In addition to being a public health crisis, the virus is infecting the global economy, he said.

Financial markets have been hard-hit by the uncertainty; global supply chains have been disrupted; investment and consumer demand have plunged, with a real and rising risk of a global recession, he warned.

UN economists estimate that the coronavirus crisis could cost the global economy at least 1 trillion U.S. dollars this year, or more, Guterres said, but warning against panic.

"This is a time for prudence, not panic; science, not stigma; facts, not fear. Even though the situation has been classified as a pandemic, it is one we can control," he said.

"We can slow down transmissions, prevent infections and save lives. But that will take unprecedented personal, national and international action," he said.

The spread of the virus will peak and the economies will recover, he said. "Until then, we must act together to slow the spread of the virus and look after each other."

Countries must cooperate to contain the virus and mitigate its damage, said Guterres. "More than ever, governments must cooperate to revitalize economies, expand public investment, boost trade, and ensure targeted support for the people and communities most affected by the disease or more vulnerable to the negative economic impacts, including women, who often shoulder a disproportionate burden of care work."

"A pandemic drives home the essential interconnectedness of our human family. Preventing the further spread of COVID-19 is a shared responsibility for us all," he added.

The United Nations, including the World Health Organization, is fully mobilized, Guterres said. "As part of our human family, we are working 24/7 with governments, providing international guidance, helping the world take on this threat. We stand in full solidarity with you."

"We are in this together, and we will get through this, together," he added.