A G20 meeting would normally be an opportunity for a U.S. secretary of state to push for support on U.S. positions.

Amid diplomatic tensions between host South Africa and the Trump Administration, the U.S. will be represented at a meeting of foreign ministers by the acting ambassador to South Africa.

The meeting will focus on Gaza and Ukraine but countries from the Global South want to confront reform, climate change and economic fairness. US FM Marco Rubio is boycotting over South Africa's "anti-American" policies.