Story highlights Hillary Clinton's campaign on Tuesday released a joint statement from 10 former Obama and Clinton administration diplomats who are questioning Bernie Sanders' ability to handle foreign policy issues

The statement comes in the wake of the Vermont senator's call at Sunday's debate to normalize relations with the longtime U.S. foe

Winterset, Iowa (CNN) Hillary Clinton's campaign on Tuesday released a joint statement from 10 former Obama and Clinton administration diplomats who are questioning Bernie Sanders' ability to handle foreign policy issues, including working with Iran and fighting ISIS.

The statement comes in the wake of the Vermont senator's call at Sunday's debate to normalize relations with the longtime U.S. foe.

"The stakes are high. And we are concerned that Sen. Sanders has not thought through these crucial national security issues that can have profound consequences for our security," the diplomats said. "His lack of a strategy for defeating ISIS -- one of the greatest challenges we face today -- is troubling. And the limited things he has said on ISIS are also troubling."

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Among those who signed the statement are Ambassador Wendy Sherman, the under secretary of state for political affairs who led the nuclear negotiations with Iran; Jeremy B. Bash, former chief of staff to the director of the CIA and Ambassador Nicholas Burns, former under secretary of state for political affairs.

Michael Briggs, a Sanders campaign spokesman, said that while Clinton has more experience, Sanders' "judgment on major foreign policy issues is far superior."

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