Asked by reporters in the Oval Office if the United States is going to war with Iran, Trump said, “We will see what happens with Iran. If they do anything, it’ll be a big mistake.”
He added, “If they do anything, they will suffer greatly.”
Trump made the comments before meeting at the White House with Hungary's prime minister, Viktor Orbán.
Tensions escalated in the Middle East on Friday as Iran warned it could easily destroy a naval fleet sent by the United States in order to ward off a potential threat to American commercial interests.
"Their billion[-dollar] fleet can be destroyed with one missile," Ayatollah Tabatabai-Nejad said, according to Reuters.
Last week, a Bomber Task Force was deployed to the Middle East along with a U.S. Navy fleet in an effort to counter reported threats from Iran.
"Any attack on United States interests or on those of our allies will be met with unrelenting force," National Security Adviser John Bolton said last week. "The United States is not seeking war with the Iranian regime, but we are fully prepared to respond to any attack, whether by proxy, the Islamic Revolutionary Guard Corps, or regular Iranian forces."
On Monday, Trump was also asked about two Saudi oil tankers and a Norwegian-flagged vessel being damaged in what Gulf officials described as a "sabotage" attack off the coast of the United Arab Emirates.
Emirati officials have declined to elaborate on the nature of the sabotage or say who might have been responsible. However, the reports come as the U.S. has warned ships that "Iran or its proxies" could be targeting maritime traffic in the region.
“It's going to be a bad problem for Iran if something happens, I can tell you that. They're not going to be happy. They’re not going to be happy people,” Trump said.
Asked to clarify, Trump responded: “You can figure it out yourself. They know what I mean by it.”
Fox News’ Sam Dorman and The Associated Press contributed to this report.