US President Donald Trump has called those behind the suicide bombing in Manchester "evil losers in life" who murdered "so many young, beautiful, innocent people living and enjoying their lives."

Speaking in the Middle East on his first foreign trip, Trump said he would not call those responsible "monsters, because they would like that term. They would think that's a great name.

"I will call them, from now on, losers, because that's what they are," Trump said. "They're losers, and we'll have more of them, but they're losers. Just remember that."

We stand in absolute solidarity with the people of the United Kingdom. pic.twitter.com/X6fUUxxYXE

— Donald J. Trump (@realDonaldTrump) May 23, 2017

British authorities say that at this point, they believe only one suicide attacker detonated himself at the Manchester Arena in Northern England, where Monday night's bombing took place after a concert by Ariana Grande. Investigators are trying to determine whether the attacker acted alone or was part of a wider terrorist network.

At a news conference in Bethlehem alongside Palestinian Authority President Mahmoud Abbas, Trump expressed his condolences to those affected by the attack - Britain's first suicide bombing in more than a decade. At least 22 people, including children, were killed, and 59 injured.

"We stand in absolute solidarity with the people of the United Kingdom," Trump said. "So many young, beautiful, innocent people living and enjoying their lives, murdered by evil losers in life."

He reiterated his call on Muslim nations to stamp out Islamic extremism.

"This is what I've spent the last few days talking about during my trip overseas," Trump said. "Our society can have no tolerance for this continuation of bloodshed."

Trump pledged US aid for the investigation into the attack in a telephone call Tuesday with British prime minister Theresa May. Trump is set to meet in person with May later this week.