BUENOS AIRES (REUTERS) - Agriculture ministers from the Group of 20 (G-20) countries said on Saturday (July 28) they were concerned about the increasing use of protectionist non-tariff trade measures inconsistent with World Trade Organisation (WTO) rules.

The ministers from countries including the United States and China, in Buenos Aires for the G-20 meeting of agriculture ministers, said in a joint statement they had affirmed their commitment not to adopt "unnecessary obstacles" to trade, and affirmed their rights and obligations under WTO agreements.

The meeting came amid rising trade tensions that have rocked agricultural markets.

China and other top US trade partners have placed retaliatory tariffs on American farmers after the Trump administration put duties on Chinese goods as well as steel and aluminum from the European Union, Canada and Mexico.

"We had a very frank discussion about the fact that we don't want unilateral protectionist measures," German Agriculture Minister Julia Klockner said in a press conference after the meeting.

Last week, the Trump administration said it would pay up to US$12 billion (S$16.3 billion) to help US farmers weather the trade war.

President Donald Trump and the chief of the European Commission struck a surprise deal on Wednesday that ended the risk of further escalating trade tensions between the two powers.

The ministers, whose countries represent 60 per cent of the world's agricultural land and 80 per cent of food and agricultural commodities trade, did not specify which measures they were referring to in the statement.

Asked for details, Klockner said the ministers did not want to "criticise a single country."

"We all know what happens if a single person or country doesn't adhere to WTO rules, trying to get a benefit for themselves through protectionism," she said.

"This will usually lead to retaliatory tariffs."

In the statement, the ministers said they agreed to continue reforming the WTO's agricultural trade rules.

"Independent of all the news there was surrounding (the meeting), we managed to reach a unanimous consensus," Argentine Agriculture Minister Luis Miguel Etchevehere said.

After the meeting with European Commission President Jean-Claude Juncker last week, Trump said the European Union would buy "a lot" of US soybeans.

Earlier, Klockner told Reuters that the trade relationship between the United States and the European Union was improving, but there was no guarantee the bloc would import the quantity of soybeans that Washington expects.