Antonio Guterres, former head of the UN refugee agency, took over Ban Ki-moon's post on New Year's Day with a promise to shake up the world body.
Measure drafted by Canada passes by a vote of 122 to 13 in the 193-nation assembly, with 36 abstentions. Russia, Iran and China oppose the resolution.
The sanctions, imposed by the UN Security Council, would strip the country of more than $700 million.
The UN special adviser on the prevention of genocide, who visited South Sudan last week, said there's a strong risk of violence escalating along ethnic lines with the potential for genocide.
Some 50 world leaders took part in the summit, but their participation was conditional as some 1.2 million refugees are in need of resettlement.
More concrete progress is expected at a follow-up summit on Tuesday called by US President Barack Obama, where at least 45 countries are expected to make pledges.
A Reuters report says the United Nations and the Organization for the Prohibition of Chemical Weapons found that Syrian military used chemical weapons on civilians.
Dossier adopted by the UNSC, including by Pyongyang's only ally China, says the council will "continue to closely monitor the situation and take further significant measures" if merited while calling on all sides to work to reduce tensions.
The leader of the world's youngest nation met with ambassadors of the UN Security Council to accept 4,000 additional peacekeepers to the region to avoid arms embargo.
United Nations Security Council votes to extend full restoration of its peacekeeping mission in Western Sahara.
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