Some 3.9 million people - a staggering one in three people throughout the country - are going hungry as the fighting in South Sudan continues, according to UN officials.
The Security Council described a "catastrophic food insecurity situation in South Sudan that is now the worst in the world" and said the country was on the threshold of a full-blown famine if fighting continued.
It called on countries that pledged $618m in aid for South Sudan at a conference in May to make good on their promises and to increase their commitment.
Fighting erupted in South Sudan in December, sparked by a power struggle between President Salva Kiir and his deputy Riek Machar.
The 15-member Council also condemned the latest round of fighting around the town of Nasir and reminded the warring sides that attacks against civilians may lead to war crimes prosecutions.