JEFFERSON CITY, Mo. (AP) — Gov. Eric Greitens is willing to send National Guard troops to the Mexican border if asked by President Donald Trump.

"The Governor understands how grave the security situation on our southern border is," Greitens' spokesman Parker Briden said Friday in an email. "The men and women of the Missouri National Guard stand ready to serve."

Earlier in the week, Trump directed the Department of Homeland Security and the Department of Defense to coordinate with state governors in order to place National Guard troops on the U.S. southern border with Mexico.

That coordination is crucial, because presidents can't automatically use the military for domestic law enforcement.