The resolution adopted unanimously today by the UN's most powerful body will also increase the UN's international police contingent from 900 to 1,323.
To reach the new levels, the council authorised the temporary transfer of troops, police and equipment from UN missions in Congo, Darfur, Abyei, Ivory Coast and Liberia. The UN also wants attack helicopters for South Sudan.
The council condemned the fighting and violence against civilians and ethnic communities that have caused hundreds of deaths across South Sudan, and reported human rights violations by all parties.
It called for "an immediate cessation of hostilities and the immediate opening of a dialogue".
COMMENT RULES: Comments that are judged to be defamatory, abusive or in bad taste are not acceptable and contributors who consistently fall below certain criteria will be permanently blacklisted. The moderator will not enter into debate with individual contributors and the moderator’s decision is final. It is Belfast Telegraph policy to close comments on court cases, tribunals and active legal investigations. We may also close comments on articles which are being targeted for abuse. Problems with commenting? firstname.lastname@example.org