Former Trump administration national security officials are blasting the ex-president for interfering in delicate hostage negotiations over Wall Street Journal reporter Evan Gershkovich, who was imprisoned in Russia last year.

Donald Trump has promised that Gershkovich would be released upon his election, which veterans of his own White House say could delay the reporter’s freedom and undermine U.S. democracy by encouraging Russia to hold Gershkovich until after the election to aid Trump’s campaign. Russia has accused the journalist of spying, which his family, employer, and President Biden say is false.

In a campaign ad released Tuesday, Trump boasts that if he beats Biden in November Russia will promptly return Gershkovich.