GENEVA, June 24 (Xinhua) -- The World Health Organization (WHO) said Wednesday that the number of COVID-19 cases worldwide is expected to reach 10 million within the next week, while underlining the vital role of oxygen concentrators in saving lives of severe and critical patients.

More than 9.1 million COVID-19 cases and more than 470,000 deaths have been reported to WHO, according to WHO Director-General Tedros Adhanom Ghebreyesus at Wednesday's press briefing.

In the first month of the outbreak, less than 10,000 cases were reported to WHO, but in the last month, almost 4 million cases have been reported, he added. "We expect to reach a total of 10 million cases within the next week," and "we have an urgent responsibility to do everything we can with the tools we have now to suppress transmission and save lives."

The WHO chief underlined the vital role of using oxygen concentrators as one of the most effective ways to save severe and critical COVID-19 patients' lives, as they cannot get enough oxygen into their blood by breathing normally and thus need higher concentrations of oxygen and support to get it into their lungs. Left untreated, severe COVID-19 deprives cells and organs of the oxygen they need, which ultimately leads to organ failure and death.

WHO estimates that at the current rate of about one million new cases a week, the world needs about 620,000 cubic meters of oxygen a day, which is about 88,000 large cylinders. However, many countries are experiencing difficulties in obtaining oxygen concentrators, as 80 percent of the market is owned by just a few companies and demand is currently outstripping supply.

Tedros announced that WHO and its UN partners are working with manufacturers across the world through a variety of private-sector networks to buy oxygen concentrators for countries that need them most.

Ongoing talks have enabled WHO to buy 14,000 oxygen concentrators, which will be sent to 120 countries in the coming weeks. A further 170,000 concentrators, with a value of 100 million U.S. dollars, can be available over the next six months. In addition, WHO has bought 9,800 pulse oximeters, a simple device used to monitor oxygen in a patient's blood, which are being prepared for shipment.

The WHO chief also echoed his support to a decision of Saudi Arabia to limit the number of pilgrims to join the annual Hajj pilgrimage based on COVID-19 risk assessment, and urged all countries to follow suit by putting health first.

Earlier this week, Saudi Arabia announced that this year's Hajj will proceed with a limited number of pilgrims of different nationalities who live within the country.