WASHINGTON -- The US ambassador to the United Nations ramped up pressure on China on Sunday, saying "the time for talk is over" to address North Korea's missile and nuclear programs.

Amb. Nikki Haley expressed her frustration with China earlier in the day as well, tweeting, "Done talking about NKorea. China is aware they must act."

Her remarks came two days after North Korea test-fired an intercontinental ballistic missile into waters between Korea and Japan, its second in less than a month.

"The time for talk is over. The danger the North Korean regime poses to international peace is now clear to all," she said in a statement.

The ambassador denied reports that Washington was seeking an emergency meeting of the UN Security Council in response to Friday's test, saying an additional resolution will be of no value if it does not significantly increase international pressure on the North.

"In fact, it is worse than nothing, because it sends the message to the North Korean dictator that the international community is unwilling to seriously challenge him," Haley said.

"China must decide whether it is finally willing to take this vital step."

North Korea is already subject to a slew of Security Council resolutions that punish the regime in Pyongyang for its missile and nuclear tests. The ICBMs have the range to reach the continental US if launched on a standard trajectory, according to experts.

Washington has been pushing for tougher sanctions on North Korea in the face of resistance from China and Russia.

On Saturday, US President Donald Trump openly expressed his frustration at China, saying he is "very disappointed" in the country.

"Our foolish past leaders have allowed them to make hundreds of billions of dollars a year in trade, yet they do NOTHING for us with North Korea, just talk," he tweeted. "We will no longer allow this to continue. China could easily solve this problem!"

China is North Korea's last major ally and a key supplier of food and crude oil to the impoverished nation. While Beijing has denounced Pyongyang's nuclear and missile tests, it has also been reluctant to push the regime too hard out of concern about instability on their border. (Yonhap)