Washington (CNN) The mayor of Oakland is firing back at President Donald Trump over his suggestion that the Department of Justice investigate her for obstruction of justice.

"Mr. President, I am not obstructing justice. I am seeking it," wrote Libby Schaaf, the Democratic mayor of the California city since 2015, in an op-ed published in The Washington Post on Friday.

In February, Schaaf issued a public warning for the immigrant communities in her city about impending raids by US Immigration and Customs Enforcement (ICE) agents in the San Francisco Bay Area, a move that earned her heavy criticism from the Trump administration.

"I wanted to make sure that people were prepared, not panicked, and that they understood their legal rights," Schaaf wrote Friday of her decision back in February.

Schaaf said as mayor, it's her "duty to protect my residents — especially when our most vulnerable are unjustly attacked."

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