The UN Security Council deplored the collapse of peace talks between South Sudan's warring factions, and once more threatened sanctions.
Peace talks held in Ethiopia, brokered by the east African regional bloc IGAD, have resulted in a string of broken ceasefires, and the last round of talks collapsed on March 7.
Since then, both sides have confirmed the outbreak of fresh fighting on several fronts in the country.
The Security Council has repeatedly threatened both sides with sanctions since the peace talks failed, although none has yet been imposed.
The Security Council expressed its "profound disappointment" that President Salva Kiir and his former deputy Riek Machar - whom he accuses of planning a coup - failed to agree on a deal to set up a transitional unity government.
"In this context, the Security Council reiterates its willingness to impose sanctions against those who threaten the peace, security or stability of South Sudan," the UN's international peace and security organ said in a unanimous declaration.
The punitive measures could include an arms embargo and the designation of senior officials "responsible for actions or policies that threaten the peace, security or stability of South Sudan," thus freezing their assets and barring them from travel, it added.
The Council accused Kiir and Machar of violating their obligations in pursuing hostilities.
On March 3, the Security Council adopted a resolution to set up a sanctions regime that would punish those who block peace efforts with an assets freeze and global travel ban.
A panel of experts is due to help a sanctions committee, due to meet for the first time Wednesday, designate the relevant individuals and entities.
The UN Security Council pressed the African Union to make public "as soon as possible" a report by its commission of inquiry on South Sudan.