U.S. President Donald Trump is asking Attorney General Jeff Sessions to file a federal lawsuit against certain companies that supply and manufacture opioids.

Speaking during a Cabinet meeting Thursday, Trump said he's directing Sessions to file a separate lawsuit, rather than joining existing lawsuits filed by states affected by the spread of the often-lethal, highly addictive drugs.

Trump is asking Sessions to look out for opioids coming into the U.S. from China and Mexico, saying those countries are "sending their garbage and killing our people."

Trump added: "It's almost a form of warfare."

It was not immediately clear if or when a federal suit would be filed. A barrage of suits have been filed nationwide against distributors and manufacturers in recent months amid the opioid epidemic.

On Thursday, the Trump administration also said it was proposing that U.S. pharmaceutical companies cut production of the six most abused opioids by 10 per cent next year, in an effort to reduce the number of drugs potentially diverted for trafficking.

In a joint statement, the U.S. Justice Department and Drug Enforcement Administration said the proposed reduction would be in keeping with Trump's effort to cut opioid prescription fills by one-third within three years.

The agencies said they are proposing to cut production quotas for oxycodone, hydrocodone, oxymorphone, hydromorphone, morphine, and fentanyl by seven per cent to 15 per cent in 2019.