US President Barack Obama has called for a decriminalisation of medical marijuana in a bid to promote a "public health model" for the drug on the eve of the 420 cannabis celebration day.

Appearing on CNN's special documentary series, titled Weed 3, Obama told the channel's chief medical correspondent, Dr Sanjay Gupta: "I'm on record as saying that not only do I think carefully prescribed medical use of marijuana may in fact be appropriate and we should follow the science as opposed to ideology on this issue, but I'm also on record as saying that the more we treat some of these issues related to drug abuse from a public health model and not just from an incarceration model, the better off we're going to be.

"One of the great victories of this country has been our ability to reduce incidences of smoking, increase the incidences of seat belt use... we save hundreds of thousands of lives every single year.

"We didn't throw anybody in jail; we just made sure that they were well-informed and if somebody has an addiction, we made sure that we made it easy for them to get help."

The show's host, Dr Gupta, is known to be supporter of marijuana and has previously called for a "medical marijuana revolution".

"I had my own turn around a couple of years ago, and at the time it was a lonely place to hold a supportive position on medical marijuana... just two years later, in 'Weed 3,' we are eyewitnesses to a revolution in full swing," said Dr. Gupta, reported Inquisitr.

President Obama
US President Barack Obama shows support for medical marijuana in favour of a \'public health model\' for the drug on the eve of 420 cannabis day. Reuters

"This time around, you will hear from the heads of government agencies earnestly sharing their point of view... even the President of the United States. This is what a revolution looks like."

Twenty-three US states have legalised medical marijuana as of April 2015 with nine states having a pending legislation.

Recreational use of marijuana is also legalized in four states and Washington D.C.

According to a Reuters poll, public opinion has shifted in recent years with an estimated 46 per cent of Americans now in support of a full legalization of marijuana.

4/20 fever takes over UK

More than 50 people were arrested in Hyde Park on 19 April over drugs-related offences during a 420 day celebration pro-cannabis rally in support of legalizing the drug in the UK.

"We need legal access for cannabis and medical access to cannabis especially," said Stewart Harper, the organiser of the rally.

"I can completely understand [worries about addiction] but if you regulated the market to make sure substances were not sold to children and that it was regulated then that is a better situation, rather than leaving it without control and to anarchy in the black market.

"We prefer to look at this as a health issue rather than a criminal issue. We are thinking of how we can reduce the harm rather than saying 'this is illegal'."