(AP) — President Donald Trump says he’s replacing his embattled Homeland Security Secretary Kristi Noem and will nominate in her place Oklahoma Republican Sen. Markwayne Mullin.

Trump made the announcement on social media on Thursday, two days after Noem faced a grilling on Capitol Hill from GOP members as well as Democrats.

Trump says he’ll make Nome a “Special Envoy for The Shield of the Americas,” a new security initiative that he said would focus on the Western Hemisphere.