"The cumulative actions of the DPRK [North Korea] since their last nuclear test compel us to look at a range of measures that would apply pressure," said a spokesman for the US Permanent Mission to the United Nations.
"As Secretary Tillerson said on Friday [Saturday NZT], business as usual is not an option. We are exploring options for a response to this series of provocations with our Security Council colleagues," the spokesman said. Tillerson on Saturday urged the Security Council to act before North Korea does.
The Trump Administration has been aggressively pressing Beijing to rein in its ally and neighbour North Korea, warning that all options were on the table if Pyongyang persists with its nuclear and missile development.
But China has said military threats would not help the situation and has accused the US of fuelling tensions on the Korean Peninsula.
Beijing on Wednesday reiterated its opposition to the deployment of the US Thaad anti-missile defence system in South Korea and urged it to be halted immediately.
The last round of complex sanctions imposed by the Security Council took three months to negotiate following Pyongyang's fifth nuclear test in September.
Those measures aimed to cut North Korea's annual export revenue by a quarter.
Traditionally, the US and China have negotiated new sanctions before involving remaining council members. UN diplomats said the current talks were still just between the two countries.
At a minimum, the US could push China to agree to condemn North Korea's missile launches in a resolution, instead of a statement, which may also blacklist more people and entities tied to the country's ballistic missile programme.
This is what the council did in 2013 in response to North Korea's first launch of a long-range rocket, using ballistic missile technology, in 2012.
Pyongyang said the rocket put a weather satellite into orbit.
