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.
The testimony could shed light on concerns about the security risk posed by Trump's first national security adviser.
President Donald Trump's first visit to Jerusalem as president is being overshadowed by reminders of tumult back home.
Lawmakers from both parties have said major changes will be needed as the measure moves through Congress.
Trump's blueprint for the 2018 budget year includes a wave of cuts to benefit programs such as Medicaid, federal employee pensions, welfare benefits and farm subsidies.