Trump, speaking at a prayer breakfast attended by politicians, faith leaders and guests including Jordan's King Abdullah, said he wanted to prevent a "beachhead of intolerance" from spreading in the United States.
"The world is in trouble, but we're going to straighten it out, OK? That's what I do - I fix things," Trump said in his speech.
Trump's executive order a week ago put a 120-day halt on the U.S. refugee program, barred Syrian refugees indefinitely and imposed a 90-day suspension on people from seven predominantly Muslim countries - Iran, Iraq, Libya, Somalia, Sudan, Syria and Yemen. The measure, which Trump says is aimed at protecting the country from terrorist attacks, has drawn protests and legal challenges.
Trump, a wealthy businessman and former reality TV star who had never previously held public office when he was sworn in on Jan. 20, also sought to reassure the large crowd about the nature of his phone calls with world leaders.
The Washington Post said Trump had a tense call with Australia's Prime Minister about his immigration order.
"Believe me, when you hear about the tough phone calls I'm having - don't worry about it. Just don't worry about it," Trump said. He did not specify which calls he was referring to.
"We're taken advantage of by every nation in the world virtually. It's not going to happen anymore," said Trump, who campaigned on a stance of "America first" that he said would ensure the country was not taken advantage of in its trade or other foreign relations.