Fentanyl, traditionally used in palliative care, is a synthetic opioid 100 times more potent than morphine.

It could be the dinner date that saves tens of thousands of US lives.

Key points: Some 29,400 people were killed by fentanyl-related overdoses in the US in 2017 alone

The synthetic opioid is also known by the street names "China White" or "China Girl"

While the deal was applauded in the US, Chinese state media gave it no mention

Fentanyl-related deaths are also on the rise in Australia

On the sidelines of the G20 summit in Buenos Aires, Chinese President Xi Jinping and his delegation broke bread with United States President Donald Trump and his team.

And while the post-dinner headlines focused on an important trade war ceasefire, one of the key topics of discussion was fentanyl.

After years of pressure from US officials, Mr Xi agreed to label fentanyl a controlled substance, in what White House Press Secretary Sarah Sanders labelled a "wonderful humanitarian gesture" that would see people illegally selling the drug to the US face "China's maximum penalty under the law".

Fentanyl — which also goes by the street names "China Girl" or "China White" — is a powerful synthetic opioid, roughly 100 times more potent than morphine and 50 times more powerful than heroin.

It is traditionally a prescription drug used in palliative care, providing pain relief to cancer patients and those suffering from severe chronic pain.

In its legal form, fentanyl comes in a number of different forms including slow-release patches, nasal sprays, injectable formulations, tablets, and lozenges.

But in recent years it has been heavily overprescribed and has been adapted to become a popular illicit drug that is often cut with heroin, cocaine, or methamphetamines, sometimes without the user's knowledge.

It claimed the life of Prince in 2016, and in 2017 alone more than 29,400 people in the US died due to fentanyl-related overdoses, making it the biggest driver of overdose deaths in America, according to the National Institute on Drug Abuse (NIDA).

Fentanyl is a highly controlled substance in the US, but with most of the US fentanyl supply manufactured in China, US authorities have struggled to control the flow of the drug into the country via illegal channels.

'It will save thousands of American lives'

Mr Trump, who declared opioid abuse a public health emergency in 2017 and has made curbing fentanyl use a top priority for his administration, praised Mr Xi for agreeing to rank fentanyl trafficking among China's most serious crimes.

"What he will be doing to fentanyl could be a game changer for the United States and what fentanyl is doing to our country in terms of killing people," Mr Trump said on Air Force One as he left Argentina.

Mr Trump has been extremely vocal about cracking down on the drug, slamming it in speeches and on Twitter.

China's Ministry of Foreign Affairs was far broader in their summation of the agreement, stating that China simply "has decided to sort out and manage fentanyl substances in categories, and to start the adjustment of relevant laws and regulations."

They also said in the statement that measures from China to crack down on the illegal flow of the drug have been well-recognised by the global community.

In 2017, Chinese authorities assisted the US in busting a drug trafficking group, charging two Chinese citizens who ran the operation that shipped fentanyl and 250 other drugs to at least 25 countries and 37 US states.

But while the opioid epidemic has been a central issue in America in recent years, there has been little reporting of China's connection to the problem in state media.

The news that China had agreed to more tightly control fentanyl was widely censored on major Chinese internet portals and state media site Xinhua.

CGTN's coverage also did not mention fentanyl, simply stating that the dinner meeting was positive and successful.

Days before the dinner meeting in Argentina, Chinese Foreign Affairs Ministry Spokesperson Geng Shuang told a news conference that opioid abuse is not an issue in China, like it is in the United States.

While it was kept largely under wraps in China, the move was applauded back in the US, where Republican senator and chair of the Senate's health committee Lamar Alexander praised Mr Trump for securing the agreement.

"President Trump's agreement yesterday with President Xi is the single most important step that could be taken to stop the flow of deadly fentanyl," he said.

"It will save thousands of American lives."

Fentanyl-related deaths on the rise in Australia

In September, US Drug Enforcement Administration (DEA) deputy operations chief for global operations Paul Knierim told Congress the DEA were working with China to stem the flow of fentanyl, but the street value of the drug in America continues to make it an appealing venture for criminal groups in the US, Mexico, Canada, and the Caribbean.

"Because of its low dosage range and potency, one kilogram of fentanyl purchased in China for $3,000 to $5,000 can generate upwards of $1.5 million in revenue on the illicit market with the potential of being lethal for 500,000 people," Mr Knierim said in his testimony.

Fentanyl has also become a health issue in Australia, as opioid abuse continues to increase in regional areas.

A report from the National Coronial Information Service found there were 498 fentanyl-related deaths in Australia between 2010 and 2015, marking a 1,800 per cent increase on the previous decade.

And recent data from the Australian Criminal Intelligence Commission analyses of wastewater for 12 different drugs revealed a large increase in the amounts of fentanyl in regional areas.

Though it is unclear whether the drug traces in the wastewater are from legal or illegal channels.