U.S. President Donald Trump said he has “some pretty severe things” in mind when asked about how he will respond to North Korea’s recent missile tests.

“It’s a shame they’re behaving this way. They’re behaving in a very, very dangerous manner and something will have to be done about it,” Trump said during a news conference Thursday with Polish President Andrzej Duda.

Trump said he doesn’t draw red lines but empathized he’s considering different ways to respond to North Korea’s aggression.

“As far as North Korea is concerned, I don’t know, we will see what happens,” Trump said. “I have some pretty severe things that we are thinking about. That doesn’t mean we are going to do it. I don’t draw red lines.”