The Justice Department threatened in a new memo to prosecute local officials who refuse to help President Trump carry out his immigration agenda. The directive raised the possibility of clashes between the Trump administration and Democrats in so-called sanctuary cities and states.

The memo was issued yesterday by Emil Bove, the acting deputy attorney general and a former member of Trump’s criminal defense team. The document asserts that state and local officials are bound to cooperate with the Trump administration under the Constitution’s Supremacy Clause and could face criminal prosecution or civil penalties if they failed to comply.

The move came as the Department of Homeland Security prepared to make targeted raids in cities, including Chicago, with high numbers of undocumented immigrants. It was one of a blitz of actions the Trump administration has taken on immigration, including an executive order declaring border crossings an “invasion.”

The Pentagon also said today that it would send 1,500 troops to the southwestern border by the end of the month. Several more border deployments are likely to follow, a Defense Department official said.