The aging Runit Dome, which stores radioactive waste from Cold War-era bomb tests in the Marshall Islands, is threatened by storms and rising sea level.
The threat comes on the heels of Trump's decision to pull the U.S. from a Cold War-era nuclear deal with Russia.
Russian official Sergei Ryabkov said the Trump administration was using the Cold War-era pact to “blackmail” the Kremlin.
The military drills will involve almost 300,000 troops.
Nuclear brinksmanship, threats of nuclear war, and similar uses of nuclear weapons to intimidate hold the potential for catastrophe.
Maintenance of the shelter system, which once entailed federal funding to stock shelters with food and water, ended decades ago.
"We have avoided nuclear war not through prudent leadership but good fortune," said Beatrice Fihn, at the award ceremony in Oslo.
The sirens' reactivation comes as North Korea fired a missile on Tuesday.
Policymakers should reconsider Washington’s current strategy, which needlessly risks the lives, wealth and security of Americans.