"I won't call them monsters, because they would like that term... they're losers, just remember that," he said Tuesday during a press conference with Palestinian President Mahmoud Abbas. Trump met with Abbas in Bethlehem after meeting with Israeli leaders in Jerusalem on Monday.
"We stand in absolute solidarity with the people of the United Kingdom," Trump said.
The blast at a concert by American pop singer Ariana Grande killed at least 22 people and wounded over 50, according to U.K. police. Police said the incident is "being treated as a terrorist incident."
First Lady Melania Trump also expressed sympathies for those affected by the attack.
Trump's visit to Jerusalem and Bethlehem is part of his first foreign trip as president. On Monday, he became the first sitting U.S. president to visit the Western Wall. He also met with leaders in Saudi Arabia over the weekend.
Mollie Reilly contributed reporting.