President Trump says North Korea has 'gotta behave'

— -- President Donald Trump weighed in on the tense situation with North Korea on the sidelines of the annual White House Easter Egg Roll today.

When asked for his message to North Korea after its failed missile launch on Sunday, Trump responded, "They gotta behave."

Later, when ABC News pressed Trump on his next move on the Korean Peninsula, he said, "You'll see."

Vice President Mike Pence and his family were in South Korea over the weekend, where they visited the Demilitarized Zone between the North and South.

At today's White House press briefing, press secretary Sean Spicer said Trump won't be "drawing lines in the sand" when talking about possible actions against North Korea.

"He holds his cards close to the vest. I think you're not going to see him telegraphing how he's going to respond to any military or other situation going forward. That's just something he believes has not served us well in the past," Spicer said. "So I don't think that you're going to see the president drawing red lines in the sand. I think the action that he took in Syria shows that when appropriate, this president will take decisive action."

Hours after North Korea paraded its weaponry and attempted a missile launch, Trump's national security adviser said the president will not allow Kim Jong Un’s regime to threaten the U.S.

"While it's unclear and we do not want to telegraph in any way how we'll respond to certain incidents, it's clear that the president is determined not to allow this kind of capability to threaten the United States," Lt. Gen. H. R. McMaster told ABC News' Martha Raddatz in an interview on "This Week." "Our president will take action that is in the best interest of the American people."

McMaster said the launch "fits a pattern of provocative and destabilizing and threatening behavior on the part of the North Korean regime."