WASHINGTON - The US government this week bought US$290 million (S$400 million) in supplies of a drug designed to treat blood cell injuries following radiological and nuclear emergencies as part of what it said were long-standing efforts to prepare for potential health impacts from threats to national security.

The US Department of Health and Human Services purchased the drug Nplate from Amgen.

When asked whether the purchase, announced on Tuesday, was linked to tensions with Russia following its invasion of Ukraine, an HHS spokesman said it was part of ongoing efforts to prepare for a wide range of threats including chemical, biological, radiological, nuclear, and emerging infectious diseases.

With funds from the Project Bioshield Act, a law passed in 2004, HHS supports development of diagnostics, vaccines and treatments to respond to potential health impacts of such threats. When development is successful, HHS buys the products for national preparedness.

Concerns about potential use of nuclear weapons have risen after Russian President Vladimir Putin has issued warnings in recent weeks that he is ready to use them to defend Russia, cautioning it was no bluff.

The White House has said repeatedly that it has seen no indication that Russia is preparing to use nuclear weapons despite what it calls Putin's "nuclear sabre-rattling."

President Joe Biden said on Thursday the threat by Putin to use nuclear weapons in Ukraine has brought the world closer to "Armageddon" than at any time since the Cold-War Cuban Missile Crisis.

Radiation sickness occurs when a person's entire body is exposed to a high dose of penetrating radiation, reaching internal organs in a matter of seconds. Symptoms include impaired blood clotting, which can lead to uncontrolled and life-threatening bleeding.

Amgen will maintain the supply in vendor-managed inventory, HHS said. REUTERS