China is believed to be one of the main manufacturers of synthetic drugs that have been blamed for public health crises in the US, Canada and Australia among other countries
The US-China trade war truce includes a pledge by Beijing to tackle another lucrative -- and deadly -- export: fentanyl, a potent opioid ravaging US communities.
The United States has pressed Beijing to do more to crack down on the drug, as smugglers from China are suspected of being the main suppliers of the narcotic, which is 50 times stronger than heroin.
At the weekend G20 summit in Argentina, China agreed to designate any type of fentanyl as controlled substances, with the US saying this would expose offenders to the maximum penalty under Chinese law -- capital punishment.
President Donald Trump said Wednesday the move could be a "game changer".
"If China cracks down on this 'horror drug,' using the Death Penalty for distributors and pushers, the results will be incredible!" Trump tweeted.
But experts doubt it will make a major difference.
Fentanyl production has become a "very profitable" business for Chinese traffickers, said Mike Vigil, a former chief of international operations at the US Drug Enforcement Administration.
It is going to be tough for the Chinese government to control the business, he said, "especially given the huge demand that we currently have in the United States."
China is believed to be one of the main manufacturers of synthetic drugs that have been blamed for public health crises in the US, Canada and Australia among other countries.
Getting the drug is relatively easy: buyers find fentanyl from suppliers online, pay for it with cryptocurrencies, credit cards or money transfers, and receive their order via international mail services, according to a US congressional report.
It has become a booming business for clandestine chemical labs in China, where a single kilogramme of fentanyl can produce 50 kilos of "high grade" heroin, turning a less than $10,000 investment into half a million dollars, said Vigil.
According to the US Centers for Disease Control, deaths from drug overdose in the US surged to nearly 72,000 last year -- far more than traffic accident deaths, gun-related deaths, or suicide. Fentanyl was linked to the deaths of singers Prince and Tom Petty.
- Zero tolerance -
At first glance, China does not seem like an ideal base for manufacturing and shipping fentanyl to the United States.
Scarred by its own opium crisis in the 19th century, China has a zero tolerance policy towards illicit drugs.
But chemical distributors in China have been able to dodge international and domestic law enforcement with fentanyl, which does have legal uses, such as treating extreme pain for cancer patients.
China has previously banned fentanyl variant by variant.
Savvy chemists would simply tweak their chemical formula, creating an analogue or slightly different chemical compound to bypass regulations.
China's decision to list all fentanyl-like substances could address that issue, but systemic challenges remain.
"It seems to be that China just has a huge chemical and pharmaceutical industry, and they just have too many firms and too few police to manage that industry," said Bryce Pardo, a drug policy researcher at Rand Corporation, a US-based think tank.
According to a 2015 US State Department report, China had about 400,000 chemical manufacturers and distributors.
China also has an unknown number of underground chemical labs that produce synthetic drugs. In 2015, Chinese authorities destroyed 259 labs and arrested 1,570 suspects, according to a 2017 US State Department report.
The interests of provincial and central government authorities are also misaligned, Pardo told AFP. Beijing sets the rules but turns enforcement over to local authorities, "who are incentivised to export as much product as possible."
The Chinese foreign ministry said before the G20 talks last week that it had taken measures to control 25 fentanyl analogues, increased intelligence sharing with other countries and strengthened checks of suspicious parcels.
"The US government surely has a bigger role to play in reducing the demand," ministry spokesman Geng Shuang told reporters.
"The US has time and again accused China of being a key source of the fentanyl-like substances at home, but never submitted any accurate statistics or effective evidence to the Chinese side," he said.
- 'Last bulwark' -
Even if China successfully cracks down on fentanyl, it is likely that another hub of synthetic opioid production will pop up elsewhere, experts said.
Fentanyl production could move to India, which has an enormous pharmaceutical industry and labour supply with "the technical knowhow to synthesise these chemicals," said Pardo.
Production of illicit drugs won't stop at fentanyl either.
According to China's narcotics control commission, domestic seizures of methamphetamine, ketamine and other synthetic drugs climbed by 106 percent year-on-year in 2016, and synthetic drug production was rising.
Enforcing harsher punishments won't necessarily address the growing global drug demand, said Michelle Miao, an expert on China's legal system at the Chinese University of Hong Kong.
The US "has launched the war on drugs in the past century, but what you can see now is it is a total failure," she said.
"Criminal law should be the last bulwark when things are out of control", she added. "The last measure we can do is mete out punishment, because it does not really solve the root issues."