NEGATIVE
Sentiment Analysis:
The title portrays South Africa's G20 role as facing uncertainty and challenges ('uncharted waters') due to an unexpected US action ('new curveball'), suggesting a disruptive and potentially adverse situation for South Africa.
Uncharted waters for South Africa’s G20 as US throws new curveball

Executive Summary
The United States has formally opposed South Africa's push for a G20 leaders' summit declaration during its presidency, arguing in a diplomatic note that no consensus document can be issued without its participation or agreement, amid its boycott of the Johannesburg event. South African officials dismiss this as invalid coercion by absence, vowing to proceed with present members, while allies including the UK, France, and London signal support for Pretoria's agenda. This confrontation tests the limits of US influence in global forums and the G20's consensus tradition, potentially resulting in a chairperson's statement instead and establishing a precedent for future summits.