WASHINGTON – President Trump did not rule out military action with North Korea as he insisted all options remain on the table in the face of nuclear threats from Kim Jong Un.

"Military action would certainly be an option. Is it inevitable? Nothing's inevitable," Trump told reporters at the White House. "It would be great if something else could be worked out."

Trump promised that if the U.S. does strike, "it will be a very sad day for North Korea."

Speaking at a joint news conference following his meeting with the emir of Kuwait, Trump refused to say whether he would demand that North Korea give up all its nuclear weapons, saying he did not want to reveal his negotiation strategy.

On Sunday, North Korea issued a statement that it had conducted its sixth nuclear test. To ratchet up the pressure, Trump aides have also suggested additional sanctions against countries that do business with the rogue regime, yet that could threaten U.S. relations with China, which is North Korea's biggest trading partner.

"I can tell you that North Korea is behaving badly and it's got to stop," Trump said.

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Discussing the economy earlier in the day, Trump told reporters he was open to the idea of eliminating the debt ceiling, the legally required limit that Congress periodically increases so that the government can borrow money to pay off its existing debts.

"It could be discussed," Trump said, citing the many political fights that have accompanied debt ceiling hikes in the past. "There are a lot of good reasons to do that."

The comment came one day after Trump reached agreement with Democratic congressional leaders to extend the debt ceiling and the current federal spending for three months, to mid-December, as well as a new aid package for victims of Hurricane Harvey.

Trump's agreement with Democratic congressional leaders Charles Schumer and Nancy Pelosi undercut Republicans who had wanted a longer-term spending bill and debt ceiling extension, past next year's election.

After his meeting with Sabah al-Ahmed al-Jaber al-Sabah, the emir of Kuwait, Trump lauded what he called cooperation between their two countries to fight terrorism. The two leaders also discussed economic ties, including the sale of U.S. military equipment to Kuwait.

"Every responsible nation must work together to strip (terrorism) groups of their territory, their financing," Trump said.