WASHINGTON—The State Department has formally designated the Syrian militant group Hayat Tahrir al-Sham as part of a foreign terrorist organization, a response to its growing sway in northwestern Syria.
Hayat Tahrir al-Sham is an offshoot of the Nusra Front, which the U.S. considers an affiliate of al Qaeda. Its success comes as a fresh test for President Donald Trump, who wants a quick U.S. exit from Syria.
In...