'In my opinion, this is just the beginning. It will get worse and worse because we are lax and we are foolish,' he said on 'Fox and Friends.'
Donald Trump has renewed his call for a ban on Muslims entering America in the wake of the Brussels attacks.
“This all happened because frankly there is no assimilation,” he said on Fox and Friends on Tuesday morning, just hours after the Belgian city was rocked by the blasts. "They don't want laws that we have, they want Sharia Law and you say to yourself, 'At what point? How much of this do you take?'
"What we are doing is allowing thousands and thousands of these people into our country and we are going to have nothing but problems as sure as you are sitting there.”
He added: “Brussels was a beautiful city, a beautiful place with zero crime. And now it's a disaster city. It's a total disaster, and we have to be very careful in the United States, we have to be very careful and very vigilant as to who we allow in this country. "
The attackers have not been identified but Trump linked the acts of terror to Muslim refugees and migrants who have been living in parts of Europe since escaping Syria.
“It's going to get worse and worse. In my opinion, this is just the beginning. It will get worse and worse because we are lax and we are foolish -- we can't allow these people, at this point we cannot allow these people to come into our country. I'm sorry," he said. "This is a story that just seems to be more and more happening and it's really not very pretty to watch."
President Obama took a different approach as he spoke about the attacks during a speech in Havana, Cuba on Tuesday morning.
"It is a reminder that the world must unite, we must be together ... in fighting against the scourge of terrorism," he said.
Hillary Clinton said the answer isn't closing the borders.
On the Today show, she said: “It's unrealistic to say we're going to completely shut down our borders to anyone but we have to do a much better job of tracking and following anyone who has any connection with terrorist activity.”
Her rapid response director Josh Schwerin tweeted:
Hillary Clinton statement on terrorist attacks in Brussels pic.twitter.com/uMyupclR4R— Josh Schwerin (@JoshSchwerin) March 22, 2016
The front runners addressed AIPAC on Monday night and expressed solid support for Israel. Around 18,000 people packed the Verizon Center in Washington.
Trump, who usually speaks off the cuff, used a teleprompter to keep his remarks carefully phrased.
“We will move the American embassy to the eternal capital of the Jewish people, Jerusalem. The bond between the U.S. and Israel is absolutely and totally unbreakable,” he said to a room full of applause.
He emphasized another bond: “My daughter Ivanka is about to have a beautiful Jewish baby!”
But Hillary Clinton fired back, targeting Trump's sometimes contradictory statements on Israel.
“We need steady hands. Not a president who says he's neutral on Monday, pro-Israel on Tuesday and who knows what on Wednesday because everything's negotiable,” she declared. “Israel’s security is non-negotiable!”