Trade and investment ministers of G20 member nations say there is an “urgent need” to improve the World Trade Organization (WTO) amid US plans to impose further tariffs on $200 billion in Chinese products.

In a joint statement, the ministers said they were "stepping up the dialogue" on international trade disputes, though the document did not provide any specifics on potential WTO reforms or on how trade dialogue was being promoted.

Germany’s Deputy Economy Minister Oliver Wittke said the joint declaration conveyed a powerful signal about the significance of strengthening WTO "especially in times of 'America first' and increasing global protectionism."

"We have to use this momentum," Wittke said during the single-day summit in the Argentine resort city of Mar Del Plata, adding more moves are to come when G20 leaders hold their summit in Argentina next November.

Washington has demanded that Beijing cut its $375 billion trade surplus with the US, end policies aimed at acquiring American technologies and intellectual property, and roll back high-tech industrial subsidies.

Pointing to the US trade war with China, Argentina’s Production and Labor Minister Dante Sica said, "Obviously the new tariff measures are not positive, but we need to see how things evolve."

Sica said talks on a free trade deal between the European Union and the Mercosur trade bloc of Argentina, Brazil, Paraguay and Uruguay were coming to a close, with a deal expected likely by the end of the year.

"We are in the final stages regarding the most delicate aspects of an EU-Mercosur agreement and we are concluding with the political and technical details," Sica announced.

Demonstrators burn a box covered with the US flag outside the G20 Trade and Investment Ministers Meeting in Mar del Plata, Argentina, September 14, 2018. (Photo by Reuters)

Protesters burned makeshift American flags and chanted against free trade orthodoxy and US President Donald Trump's support for his cash-strapped Argentine counterpart Mauricio Macri, whose fiscal belt-tightening has triggered a backlash from the country's working-class.

While Trump has threatened to withdraw the US from the WTO, China has called for reforms in the organization in a bid to make the global trade system fairer and more effective.

The 23-year-old trading institution is run on the basis of consensus, which means that every one of its 164 members has an effective veto and it is nearly impossible to reach consensus on any change to the rules.

Argentina holds the G20's rotating presidency this year, and is re-negotiating a $50 billion stand-by financing deal with the International Monetary Fund (IMF), slashing its fiscal deficit targets and reducing costs to ensure it can continue paying its international debts.