President Trump administered a warning cautioning Iran stop testing ballistic missiles, but didn't disclose what actions the U.S. would pursue. In the warning, Trump also said that Tehran must stop supporting Houthi rebels in Yemen. Michael Flynn, Trump's national security adviser, denounced Iran's behavior, accusing the country of causing instability in the Middle East. "As of today, we are officially putting Iran on notice," Flynn said from the White House podium. The warning is an example of Trump's commitment to a stricter approach to Iran.