Biden says Trump's criticism of Denmark and other NATO allies is not only embarrassing but is "making the American people less safe."
The scathing statement from the president's would-be Democratic rival comes hours before Trump's departure for the G7 summit in Biarritz.
Biden is also criticizing Trump for saying he'd be open to re-admitting Russia to the group after its 2014 expulsion over its invasion of Ukraine.
Biden says Trump's "incompetence threatens to permanently reduce America's standing."
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