US President Donald Trump has pledged to introduce a new system that will help decrease the pricing of drugs and increase competition in the pharmaceutical industry.

Without disclosing the details of the plan, Trump tweeted: "I am working on a new system where there will be competition in the drug industry. Pricing for the American people will come way down!"

After the tweet, shares of pharmaceutical and biotechnology companies such as Pfizer, Merck & Co and Amgen fell.

The latest tweet comes after a Republican bill to repeal and replace the Affordable Care Act, known as Obamacare, was unveiled.

In a previously announced plan, Trump pledged to cut 75% to 80% of the US Food and Drug Administration’s regulations.

"I am working on a new system where there will be competition in the drug industry. Pricing for the American people will come way down."

Speaking to Congress last week, Trump noted that a significant amount of effort was required to decrease the ‘artificially high’ prices for prescription drugs.

Meanwhile, House Committee on Oversight and Government Reform Ranking Member Elijah E. Cummings said that over the past ten years, 90% of brand name drugs have doubled in price, and prescription drug spending reached $348bn last year.

Cummings said: "The President promised, both during the campaign and after, that he would support efforts to stem the skyrocketing prices of prescription drugs, so I am looking forward to discussing ideas he said he supports. 

"Our hope is that the President will make good on his promise and join us in convincing congressional Republicans to finally start helping American families who rely on these life-saving medications."