ZURICH — Chinese President Xi Jinping and his Swiss counterpart, Guy Parmelin, are due to sign an upgraded trade accord in Beijing on Friday, formalizing one of the most favorable trade deals Beijing has granted a European country and bucking a broader global shift towards protectionism.

The agreement gives Switzerland unusually free access to the Chinese market, standing in contrast to the trade barriers erected not only by the US administration but, increasingly, by the European Union. Chinese and Swiss officials announced the deal in August, one year after US President Donald Trump saddled Switzerland with the highest US trade tariffs in Europe.

“This gives Switzerland better market access to China, but it’s also very important for China to show there’s a country willing to lower barriers with China in the heart of Europe,” said Bernardino Regazzoni, a former Swiss ambassador to China.

A season of high-level visits

Mr. Parmelin is in China at the same time as Germany’s president, and follows the EU’s top trade official, who traveled to Beijing earlier this month. Over the past 12 months, the leaders of the United States, Canada, Britain, France and Germany have all visited China.

Three current Western diplomats said they saw in China’s deal with Switzerland a bid to burnish its free-trade credentials and project a more internationalist image as the Trump administration steps back from multilateralism under its America First policies.

The degree of openness surprised diplomats: 99.8% of Swiss exports will gain duty-free access to China, up from just over half previously, even though the terms largely reciprocate what Bern already grants Chinese goods.

No new advantages for China

The accord raised eyebrows in Washington, and US officials sought to discuss it with their Swiss counterparts, according to two people familiar with the matter. The Swiss State Secretariat for Economic Affairs said the government regularly discusses trade policy developments with partners and that no specific concerns had been raised about the deal.

The secretariat noted that the agreement does not grant Chinese industrial goods new tariff benefits. Instead, it tackles imbalances in the initial accord and expands Swiss market access to China. The US State Department and the Office of the US Trade Representative did not reply to requests for comment.

Roger Gschwend, a senior Swiss trade official, said the deal was targeting a level playing field for Switzerland and that China wanted to show its commitment to rules-based trade. “It’s China sending a signal they are opening up their markets a bit more,” he said. China’s government did not respond to requests for comment.

Navigating a fragmented landscape

After coping with 39% US tariffs for months, Switzerland struck a provisional deal with Mr. Trump last November that cut those duties to 15%. Bern has been working to ensure its agreements hold and that it does not face new US tariffs.

The Swiss-China deal nonetheless set off some alarm bells that the improved trading terms could make Switzerland a Chinese bridgehead in Europe just as many European firms are under increased competitive pressure from China, the sources added.

The Swiss government said the accord is not expected to have any impact on bilateral goods trade between Switzerland and the EU, the United States, or other partners. Mr. Gschwend said Switzerland has not been a re-export hub for Chinese goods, nor did he see it becoming one in the future. He added, however, that the deal had piqued the interest of other countries eager to secure favorable terms from China.

Swiss companies have welcomed the agreement. Jean-Philippe Kohl, vice director of the Swiss industry association Swissmem, called it “a very, very good outcome.”

Nicola Tettamanti, owner of Tecnopinz, a maker of components for factory machines, said the deal provides stability in a world where trade uncertainty has grown — something particularly important for export-dependent Switzerland. He expects Tecnopinz’s demand from China to rise, and also sees customers such as watchmakers and robotics firms benefiting, saying the deal helps Switzerland in a fragmented geopolitical landscape.

“But we have to be careful about being caught in crossfire between the EU and China, and between Washington and Beijing,” he said.

— Reuters