US Treasury secretary Janet Yellen defended the global dominance of the dollar after leaders of some of the world’s largest emerging markets questioned the outsized role of the world’s premier reserve currency in global trade.

South Africa’s President Cyril Ramaphosa at a finance summit in Paris on Friday appeared to back calls from Brazil’s president Luiz Inácio Lula da Silva for emerging markets to review their reliance on the greenback. Lula, who appeared on a panel with South Africa’s leader, has advocated switching to trading in their domestic currencies and other alternatives.

After Lula argued the international use of the dollar put countries such as Brazil at a disadvantage, Ramaphosa said “the issue of currency” would be “on the agenda” for the upcoming meeting of Brics countries later this year. South Africa is due to host the meeting, which also includes Brazil, Russia, India and China, in August.