US President Donald Trump has said he would like to solve the North Korea crisis diplomatically, but that a "major, major conflict" is possible.
China's foreign minister called for negotiation and dialogue.
The UN Security Council is meeting to discuss North Korea on Friday and will consider further measures to counter its nuclear and missile programmes.
The country has made several military shows of strength in recent weeks but a missile it was testing failed.
America sent warships to the region and began installing a controversial anti-missile system in South Korea earlier this week.
US Secretary of State Rex Tillerson said Washington would negotiate with North Korea with a view to removing nuclear weapons from the country, not changing the government.
He told NPR radio in the US: "We do not seek regime change, we do not seek a collapse of the regime, we do not seek an accelerated reunification of the peninsula.
"We seek a denuclearised Korean peninsula - and that is entirely consistent with the objectives of others in the region as well."
North Korea has carried out repeated missile tests in recent months and is threatening to conduct its sixth nuclear test.
Mr Tillerson also indicated that he thought China, North Korea's major ally, might be starting to see the regime as a "liability" or a security risk.
"What China is beginning to re-evaluate is whether North Korea is any kind of an asset to them, or whether North Korea themselves and the regime have become a liability to China's own security," he said.
Shortly after being elected, Mr Trump accused China of not doing enough to rein in North Korea and suggested the US could take unilateral action.
But Chinese Foreign Minister Wang Yi has warned that tensions on the Korean peninsula risk getting out of control, and ahead of Friday's meeting he said negotiations with North Korea are "the only right choice".
According to Mr Tillerson, China has told the US it will impose sanctions on North Korea if it conducts further nuclear tests.
In a wide-ranging interview inside the Oval Office, Mr Trump praised China's President Xi Jinping for his handling of North Korea, calling him "a very good man" who loved his country.
He said Mr Xi "certainly doesn't want to see turmoil and death".
"He is a very good man and I got to know him very well," he said.
"He loves China and he loves the people of China. I know he would like to be able to do something, perhaps it's possible that he can't."
Mr Trump also said it had been "very hard" for Kim Jong-un to take over North Korea at such a young age.
He said: "He's 27 years old. His father dies, took over a regime. So say what you want but that is not easy, especially at that age."
But he stressed he was "not giving him credit", and added: "I hope he's rational."
"There is a chance that we could end up having a major, major conflict with North Korea. Absolutely," said Mr Trump.(Source: CNN)