"The cumulative actions of the DPRK since their last nuclear test compel us to look at a range of measures that would apply pressure," the spokesperson for the US mission to the United Nations said Tuesday.
"We are exploring options for a response to this series of provocations with our Security Council colleagues."
Diplomats said the United States was in discussion with China on the council response, including possibly sanctions, to Saturday's failed missile launch.
The United States initially sought a statement of condemnation, but the discussions shifted to targeted sanctions and possibly a draft resolution with tougher measures, diplomats said.
North Korea on Saturday carried out a failed missile launch, just hours after US Secretary of State Rex Tillerson urged the council to impose new sanctions, warning that a failure to act could lead to "catastrophic consequences."
The latest failed launch "only reinforced our resolve" to increase the economic and diplomatic pressure on North Korea, said a Security Council diplomat.
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 since 2006, two of them last year.
A shift from China
Washington has repeatedly called for stronger UN sanctions, but wants China, North Korea's main trading partner and ally, to toughen its approach.
"The Chinese are very concerned and they are increasing the pressure," said the diplomat, who spoke on condition of anonymity. "Definitely, my assessment is that they have shifted."
Over the past 11 years, the Security Council has imposed six sets of sanctions on Pyongyang -- two adopted last year -- to significantly ramp up pressure and deny Kim Jong-Un's regime the hard currency revenue needed for his military programs.
On Monday, North Korea said it will carry out a nuclear test "at any time and at any location" set by its leadership, fueling fears in the region of an escalation.
At the council meeting on Friday, Tillerson called on all countries to downgrade or sever diplomatic relations with North Korea and impose targeted sanctions on entities and individuals supporting its missile and nuclear program.
The US chief diplomat pushed for a ban on North Korea foreign workers sent abroad to earn hard currency for Pyongyang, and cutting off all North Korean imports, especially coal.
In November, the council adopted the toughest-ever sanctions on North Korea, imposing a cap on coal exports among other measures, but the measure took three months of negotiations between the United States and China.
A council diplomat said the talks between the United States and China were unlikely to yield results in the coming days.
UN experts have reported to the council that the series of sanctions have had little impact on Pyongyang, which has forged ahead with its nuclear and ballistic missile program.
US President Donald Trump on Monday said he would be "honored" to meet Kim Jong-Un in a move a UN diplomat described as a "carrot" dangled in front of Pyongyang if it changes course and halts its military programs.
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