US President Donald Trump has declared America’s opioid crisis a “national shame” as he declared it a public health emergency.

Mr Trump announced a plan to target the abuse of opioids, promising federal funding to help states combat the drug scourge.

According to the US Centres for Disease Control and Prevention, opioids were responsible for more than 33,000 US deaths in 2015.

Nearly half of all the US opioid overdose deaths in 2015 involved prescription medications.

“More people are dying from drug overdoses today than from gun homicides and motor vehicles combined,” Mr Trump said on Thursday at the White House.

“These overdoses are driven by a massive increase in addiction to prescription painkillers, heroin and other opioids.

“The United States is by far the largest consumer of these drugs using more opioid pills per person than any other country by far in the world.

“As Americans we cannot allow this to continue.”

White House officials have also said they would urge Congress, during end-of-the year budget negotiations, to add new cash to the Public Health Emergency Fund, which currently contains just $US57,000 ($A70,000), according to the Department of Health and Human Services.

‘It’s really, really easy not to take ’em’: Trump

Mr Trump’s audience overnight included parents who have lost children to drug overdoses, people who have struggled with addiction, and first responders whose have used overdose reversal drugs to save lives.

Mr Trump also spoke personally about his own family’s experience with addiction: His older brother, Fred Jr, died after struggling with alcoholism — it is the reason the US President does not drink.

During his speech, Mr Trump described his brother as a “great guy, best looking guy,” with a personality “much better than mine”.

“But he had a problem, he had a problem with alcohol … I learned because of Fred.”

Mr Trump said he hoped a massive advertising campaign, which sounded reminiscent of the 1980s Just Say No campaign, might have a similar impact.

“If we can teach young people, and people generally, not to start, it’s really, really easy not to take ’em,” he said.

– with wires