U.S. President Donald Trump could still possibly walk away from the negotiating table with China if he isn’t satisfied at the progress of talks between the two countries to resolve their trade war, according to a senior Trump administration official. The official, who spoke on condition of anonymity, said both sides were eager to reach an agreement, but significant issues were still unresolved ahead of the next round of trade talks which will get under way in Beijing on April 30 between U.S. Trade Representative Robert Lighthizer, Treasury Secretary Steven Mnuchin and Chinese Vice Premier Liu He. Discussions include intellectual property, forced technology transfer, non-tariff barriers, agriculture, services, purchases, and enforcement, according to a White House statement. Liu will then lead a Chinese delegation to Washington for additional discussions starting on May 8. Negotiators have indicated they are close to a deal and U.S. President Trump said Chinese President Xi Jinping would visit the White House “soon.”

The year-long trade war has weighed on confidence and dented shipments, with nine of the 10 gauges tracked by Bloomberg to assess the health of global trade below their average midpoint. Still, the world’s two biggest economies recently posted better-than-expected gross domestic product reports for the first quarter. Last week, the Trump administration said China had failed to bolster protection for intellectual property and open its market to more foreign companies, despite Beijing’s promises to reform. The U.S. kept China on a “priority watch list” of nations that don’t adequately protect IP rights, according to the annual report of the U.S.Trade Representative’s office on IP practices around the world.

Veteran negotiators warned that deals can often get lost in translation. Complications can arise from issues of language, interpretation and translation during negotiations. While both sides are negotiating in their native tongues with the help of simultaneous translation, the subsequent text will be translated into both English and Chinese. These translations will then be “scrubbed” by lawyers and technical translators in an effort to reach a final text that both sides are happy with. But history shows that this is rarely straightforward as ambiguity is hard to avoid in international trade deals, while experienced negotiators have said that trying to iron out arguments over words, phrases or even grammar can be “worse than pulling teeth”.

“It is very hard to enforce anything under the Chinese because their system is both complicated and relatively opaque, and there aren’t that many Mandarin speakers around that have the requisite technical trade and legal skills,” said Elena Bryan, who spent 17 years negotiating trade deals for the Office of the U.S. Trade Representative (USTR), and who now runs consultancy Pilot Rock Global Strategies. According to one account, the two sides had debated the suitability of a single word for two hours during agriculture talks via video conferencing. After failing to reach an agreement, they had to put it aside and move onto other topics, the South China Morning Post reports.