After 20 years of trying, the European Union on Friday finally reeled in its biggest trade deal by striking an accord with the South American Mercosur bloc.

The political deal will give the European Commission something to brag about at the summit of G20 leading economies in Osaka, where the EU’s free-trade agenda is finding itself increasingly isolated in the face of U.S. protectionism and Russian President Vladimir Putin’s assertions that liberalism has had its day.

Indeed, only moments after the deal was struck, European Commission President Jean-Claude Juncker said in a statement that it was a “historical moment” precisely because of the fevered global debate. “In the midst of international trade tensions, we are sending today a strong signal with our Mercosur partners that we stand for rules-based trade,” he said.

Also suggesting that the world is fracturing along ideological lines on openness to trade, European Commissioner for Trade Cecilia Malmström added: "This agreement adds four more countries to our impressive roster of trade allies.”

The four Mercosur nations are Argentina, Brazil, Paraguay and Uruguay.

The deal is the EU's biggest in terms of tariff reduction, which will come as a catalyst to many traditional industries.

Any European celebrations in Japan may be short lived, however. The EU will still need to sell the deal to skeptical countries and parliamentarians, who could well lay down hurdles if the agreement — which centers on a trade-off between cars and cows — is seen as posing a threat to farmers and the environment.

While the Commission has an exclusive competence to negotiate EU trade deals, the agreement will still need approval from member countries and the European Parliament, not to mention potentially 40 or so national and regional assemblies.

The deal is the EU's biggest in terms of tariff reduction, which will come as a catalyst to many traditional industries. It will strip away some €4 billion of duties each year, over an area with a population of 780 million people.

Mercosur countries are commiting to withdraw high tariffs on cars (35 percent), machinery (up to 20 percent) and chemicals (up to 18 percent).

Farmers on the line

Europe's challenge comes in the agricultural sector, however, as it will have to open its market to the highly competitive beef of the Argentine Pampas and sugar cane from Brazilian plantations. Europe's main farm lobby, Copa-Cogeca, warned before the deal that the Mercosur "endgame" should not mean "game over" for the European farm model.

European Commissioner for Agriculture Phil Hogan accepted that the deal presents "some challenges" to European farmers, but countered that they should be able to export premium products more effectively thanks to an agreement on protections for iconic food names ranging from Italy's Parma ham to France's Comté cheese.

Europe's food producers should also benefit from the dropping of tariffs on spirits (up to 35 percent), wines (27 percent) and confectionery (20 percent).

European ethanol producers see no upside, however, and warned the deal threatens to "trade away" their business. Emmanuel Desplechin, secretary-general of ePURE, the European renewable energy association, said his industry is being thrown "under the bus."

Crucially, the deal does ensure that both parties should hold fast to the Paris climate agreement, although this has become a contentious topic in recent days.

Officials in Osaka told POLITICO that U.S. President Donald Trump has been pushing countries such as Brazil, Turkey, Saudi Arabia and Australia to row back on climate commitments.

The rate of deforestation under Brazilian President Jair Bolsonaro has caused grave concern among environmentalists, and French President Emmanuel Macron warned him that the Mercosur deal would effectively be over if Brazil reneged on the Paris accord. "We’re asking our farmers to stop using pesticides, we’re asking our companies to produce less carbon, that has a competitiveness cost,” he explained.

Greenpeace complained that cattle are the main driver of deforestation, and that 63 percent of razed areas were given over to animal pasture.

“Trading more cars for cows is never acceptable when it leads to the destruction of the Amazon, attacks on indigenous peoples," said Naomi Ages from the campaign group.

Reporting by Hans von der Burchard, Maxime Schlee, Jakob Hanke, Eddy Wax, Zosia Wanat and Christian Oliver.