NEW YORK (Reuters) -South African President Cyril Ramaphosa said on Tuesday his country is in talks with a U.S. trade representative to reduce tariffs levied by U.S. President Donald Trump after telling world leaders that "trade is now being used as a weapon."

The U.S. is South Africa's second-biggest trading partner. Trump in August imposed a 30% tariff on imports from South Africa after Ramaphosa's government made several unsuccessful attempts to secure a trade agreement.

"We want tariffs that President Trump is seeking to levy on us and has already started, to be reduced," Ramaphosa told the Council on Foreign Relations in New York. 

Ramaphosa likened trade to a weapon earlier in the day, in remarks delivered at the U.N. General Assembly.

"Geopolitical shocks and unprecedented trade policy volatility are destabilizing the global economy and jeopardizing a critical source of development finance," he said. "In fact, trade is now being used as a weapon against a number of countries in the world."

Ramaphosa also said the African Growth Opportunity Act (AGOA) treaty should continue, a preferential trade deal, offering duty-free quota-free access for thousands of products for 32 African nations. Last year, AGOA did not get a vote in Congress.

Trump's return to the White House in January has further cast doubt on an extension, due to his tariff-driven trade stance.

South Africa, the continent's most industrialized economy, enjoyed the lion's share of the benefit. 

(Doyinsola Oladipo in New York; Editing by Chris Reese and David Gregorio)