US Secretary of State Rex Tillerson said North Korea must "earn its way back to the table" for negotiations between the two countries to restart.
Mr Tillerson said Pyongyang had to carry out a "sustained cessation" of weapons testing before any talks.
It is a U-turn from comments made earlier this week, when Mr Tillerson said the US was "ready to talk any time North Korea would like to talk".
That remark was swiftly contradicted by the White House.
North Korea has carried out repeated nuclear and ballistic missile tests this year, in defiance of global condemnation and increasingly heavy international sanctions.
Earlier this week Mr Tillerson said: "Let's just meet and let's talk about the weather if you want and talk about whether it's going to be a square table or a round table if that's what you're excited about.
"Then we can begin to lay out a map, a road map, of what we might be willing to work towards."
But his remarks, welcomed by China and Russia, were promptly greeted with a rebuttal from the White House and a reiteration that North Korea must admit to abandoning its nuclear weapons before talks resume.
Within just a few hours press secretary Sarah Saunders released a statement to reporters saying Mr Trump's views "have not changed".
"North Korea is acting in an unsafe way not only toward Japan, China, and South Korea, but the entire world," she said.
On Friday, Mr Tillerson also urged Russia and China to put more pressure on Pyongyang by taking action beyond mere compliance with UN Security Council resolutions. Both countries rejected this.
He told the UN Security Council that diplomatic options remained open, but that the US would not bow to North Korean conditions for negotiations.
"We do not accept any relaxing of the sanctions regime as a precondition of talks," he said.
"We do not accept the resumption of humanitarian assistance as a precondition of talks. So we are not going to accept preconditions for these talks."
Also on Friday at the Security Council:
- Japan's Foreign Minister Taro Kono said North Korea was not ready to talk and was "nowhere near ready" to stop developing weapons
- UN Secretary General Antonio Guterres said it was time to reignite and strengthen communication channels with Pyongyang in order to pursue diplomacy and avoid conflict, the risk of which was being multiplied due to dangerous rhetoric
- North Korean Ambassador Ja Song Nam said the Security Council session, focusing on North Korea's nuclear programme, was "a desperate measure plotted by the US being terrified by the incredible might of our Republic that has successfully achieved the great historic cause of completing the state nuclear force"
