The White House said Trump, who called May from Jerusalem, offered US assistance in the investigation of the attack late yesterday at a packed pop concert in Manchester.
"The two leaders agreed that this attack --which targeted teenage children and their friends at a joyous event -- was particularly wanton and depraved," the White House said.
"The president reassured the prime minister that Americans stand with the people of the United Kingdom and that our resolve will never waiver in the face of terrorism," it said.
British police arrested a 23-year-old man in connection with the attack, which the Islamic State group claimed was carried out by "one of the caliphate's soldiers."
The suicide bomber detonated an explosive device near an exit to the 21,000-person capacity Manchester Arena where US pop star Ariana Grande was performing to a sold-out audience.
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