An explosion struck an Ariana Grande concert attended by thousands of young music fans in northern England, killing at least 22 people and injuring dozens more.
Lawmakers from both parties have said major changes will be needed as the measure moves through Congress.
The testimony could shed light on concerns about the security risk posed by Trump's first national security adviser.
Emergency crews are on the scene of a crash that shut down parts of FM 179. The intersection of FM 179 at County Road 6400 (Urusline St.) is closed to all traffic from there north towards the accident scene.