The United States and China are discussing next steps in response to North Korea's missile tests and could reach a decision on new sanctions this week, Washington's UN envoy Nikki Haley has said.

China is pushing Pyongyang through back channels to change its behavior and discussing with the United States the timing of a possible new sanctions resolution, Haley yesterday told reporters.

"It's about at what point do we do the resolution… at what test model do we say now is the time to go forward," she said.

"We do think they are trying to counter what is happening now and they have the lay of the land," Haley said of the Chinese government.

"We are going to keep the pressure on China but we will continue to work with them … and I think we will decide this week on what that looks like."

North Korea has carried out three missile tests in less than three weeks, defying UN warnings that it faces new sanctions.

Yesterday, Pyongyang test-fired a short-range missile that fell provocatively close to Japan.

The United States launched talks on new sanctions with China a month ago with a view to drafting a proposed resolution to present to the council, but no text has been agreed.

Haley said the council was not backpedalling but rather carefully considering the next moves.

"Nothing is changing North Korea's actions and so it's regrouping and saying okay, what are we going to do if this is going to happen every other day," said Haley.

"How should we respond in a way that actually stops these things or slows them down?" she added.

China has pushed for a revival of the six-party talks that have been dormant since North Korea walked out on the negotiations in 2009.

Haley has said that the United States will open a dialogue with Pyongyang if it halts its missile and nuclear tests.

North Korea is seeking to develop a long-range missile capable of hitting the US mainland with a nuclear warhead, and has so far staged five atomic tests, two of them last year.

The Security Council adopted two sanctions resolutions last year to ramp up pressure on Pyongyang and deny leader Kim Jong-Un the hard currency needed to fund his military programs.

In all, six sets of sanctions have been imposed on North Korea since it first tested an atomic device in 2006.