WASHINGTON >> White House Chief of Staff John Kelly said today the North Korean nuclear and missile threat is “manageable” for now but the isolated nation can’t be allowed to develop the ability to strike the U.S. homeland.

Although President Donald Trump recently declared his top diplomat was “wasting his time” trying to negotiate with the North, Kelly said he hopes diplomacy works before the nation can develop its weapons capabilities further.

Kelly comments at a White House news conference were milder than Trump’s recent pronouncements. Over the past three weeks the president has exchanged threats and personal insults with North Korean leader Kim Jong Un, escalating tensions.

Kelly said that Americans should be concerned about North Korea. He said the North has developed a “pretty good” intercontinental ballistic missile capability and is developing a nuclear re-entry vehicle, which is needed for a missile to survive re-entry into the Earth’s atmosphere. Then he spelled out a bottom line.

“I think I speak for the administration, that that state can simply not have the ability to reach the homeland,” Kelly said.

He said there’s already “great concern” about Americans who live in Guam. North Korea in August threatened to fire a salvo of intermediate range missiles toward the U.S. Pacific island territory, a major military hub and home to U.S. bombers that periodically fly missions over the divided Korean Peninsula.

“Right now we think the threat is manageable,” he said, but added the situation would become more problematic over time if North Korea’s capability “grows beyond where it is today.”

“Let’s hope that diplomacy works,” he said.

Trump on Wednesday conceded differences on North Korea with Secretary of State Rex Tillerson, who advocates keeping open the possibility of negotiations with Kim’s authoritarian government.

“I think perhaps I feel stronger and tougher on that subject than other people,” Trump said in the Oval Office. “But I listen to everybody and ultimately I will do what’s right for the United States and really what’s right for the world,” he said, adding, “it’s a problem that has to be solved.”

Trump has hinted at a preference for military options, although a strike on North Korea could leave close U.S. ally South Korea vulnerable to North Korean military retaliation.