At the heart of President-elect Donald J. Trump’s threat on Monday to slap China with new tariffs is a bitterly recurring issue: the flow into the United States of the potent opioid fentanyl, created using chemicals made in China.

候任总统特朗普周一威胁要对中国征收新关税，其核心是一个反复出现的问题：使用中国制造的化学品生产的强效阿片类药物芬太尼流入美国。

But cooperation on fentanyl — to some degree, at least — between the countries has already been happening, making it one of the few issues left that the two superpower rivals have been able to make progress on.

但两国间在芬太尼问题上的合作——至少在某种程度上——已经开始，也是两个超级大国竞争对手之间能够取得进展的极少数问题之一。

In September, Chinese officials expanded the list of so-called precursor chemicals used in making the drug, imposing more oversight. The move was the result of renewed bilateral talks on narcotics that started after President Biden and China’s top leader, Xi Jinping, met in Woodside, Calif., a year ago.

今年9月，中国官员扩大了用于制造这种药物的所谓前体化学品清单，加强了监管。这是拜登总统和中国最高领导人习近平一年前在加利福尼亚州伍德赛德会晤后重新开始的双边禁毒会谈的结果。

It was a rare instance of cooperation from China, which has otherwise stonewalled the United States on issues including nuclear arms control, support for Russia and human rights. China is the main source of chemicals used to make fentanyl, a synthetic opioid that kills tens of thousands of Americans a year. Much of the flow into the United States is from drug cartels in Mexico who mix the precursors and smuggle the finished product across the border.

这种合作很罕见，在核军备控制、支持俄罗斯和人权等问题上，中国一直不予配合。芬太尼是一种合成阿片类药物，每年导致数以万计的美国人死亡，中国是用于制造芬太尼的化学品的主要来源地。大部分流入美国的毒品来自墨西哥的贩毒集团，他们混合前体，然后将成品走私过境。

Despite the recent momentum, experts have warned that much still needed to be done. Chinese producers of fentanyl ingredients, which are also used to produce legal pharmaceutical drugs, can circumvent laws by developing new uncontrolled precursor chemicals. Experts at the Council on Foreign Relations say that Chinese and U.S. law enforcement officials need to work together more closely, and that China needs to provide the United States with more support in anti-money laundering efforts to block the flow of illicit money funding the trade.

尽管最近有取得进展的势头，但专家们警告，仍有许多工作要做。芬太尼原料成分也可用于生产合法药品，中国生产商可以开发不受管制的新前体化学品，从而规避法律。美国对外关系委员会的专家表示，双方执法官员需要更加密切地合作，中国需要在反洗钱方面向美国提供更多支持，以阻止为该贸易提供资金的非法资金流动。

Some analysts were concerned that tariffs might hurt that effort more than help it.

一些分析人士担心，关税对于这一努力来说可能伤害大于帮助。

“An imposition of tariffs is not going to do anything regarding the flow of fentanyl,” said Vanda Felbab-Brown, a senior fellow at the Brookings Institution and an expert on global drug policy. “In fact, it might undermine the counternarcotics cooperation that the U.S. and China have been doing in 2024 and that came after no cooperation for over two years.”

“征收关税不会对芬太尼的流动产生任何影响，”布鲁金斯学会高级研究员、全球毒品政策专家万达·费尔巴布-布朗说。“事实上，这可能会破坏美中在2024年开展的禁毒合作，在此前两年多的时间里，双方未合作。”

Chinese officials have tended to use the fentanyl issue as leverage over the United States, cooperating only when they receive something in return.

中国官员倾向于利用芬太尼问题作为对付美国的筹码，只有在得到回报的情况下才会合作。

To restart talks on narcotics after Mr. Biden and Mr. Xi met in California, Washington agreed to Beijing’s demand that U.S. sanctions be lifted on a forensics institute run by China’s Ministry of Public Security. The institute was placed on a trade blacklist in 2020 because it was linked to abuses against ethnic minorities in China, particularly the Uyghurs. The Biden administration said the move was justified because China had shut down some companies exporting fentanyl precursors and closed their bank accounts.

拜登和习近平在加利福尼亚会面后，为了重启毒品问题谈判，华盛顿同意了中国政府的要求，即取消美国对中国公安部管理的一家司法鉴定机构的制裁。该机构因涉及中国对少数民族（尤其是维吾尔族）的虐待，于2020年被列入贸易黑名单。拜登政府表示，此举是合理的，因为中国已经关闭了一些出口芬太尼前体的公司，并关闭了它们的银行账户。

“If the United States wants to get more cooperation from China on the domestic fentanyl issue, it should seek China’s support in a constructive way instead of using unilateral, punitive measures to force China to make concessions,” said Song Guoyou, an American studies expert at Fudan University in Shanghai.

上海复旦大学美国研究专家宋国友称：“如果美国希望在国内芬太尼问题上得到中国的更多合作，它应该以建设性的方式寻求中国的支持，而不是用单方面的惩罚性措施迫使中国做出让步。”

This is not the first time that China has agreed to help crack down on fentanyl. In 2019, Beijing introduced a ban of the drug, leading the Trump administration to thank Mr. Xi for what it called “a wonderful humanitarian gesture.” Chinese and American law enforcement agents also began coordinating efforts to catch traffickers. But tensions over technology and trade, and the shooting down of a Chinese surveillance balloon over the United States, soon put an end to cooperation.

这不是中国第一次同意帮助打击芬太尼。2019年，中国政府出台了一项禁毒令，特朗普政府因此感谢习近平做出了“令人赞叹的人道主义姿态”，双方的执法人员也开始协调抓捕毒贩。但美中在技术和贸易问题上的紧张关系，以及美国上空击落一架中国侦察气球的事件，令合作很快告终。

China has long deflected blame for America’s fentanyl crisis, saying the fault lies with U.S. government policies. It also casts itself as a victim of drugs, pointing to Britain’s exploitative opium trade during the 19th century.

长期以来，中国一直称美国的芬太尼危机是美国政府的政策所致，责任不在自己。它还提起英国19世纪剥削性的鸦片贸易，把自己描绘成毒品的受害者。