The US administration announced Monday a new proposal to require drugmakers to list prices of medicines that cost more than $35 per month in television ads.

The proposal, unveiled by US Health and Human Service Secretary Alex Azar, aims to add information on prices to television spots, which typically contain extensive warnings about a medicine's side effects, but not on price.

Azar said the policy seeks to address a pricing system that is 'completely opaque' to consumers.

'List prices matter to American patients,' he said in a speech at the National Academy of Medicine. 'I've heard it personally from patients myself, and so has the President.'

Dozens of drugmakers will start disclosing the prices for US prescription drugs advertised on TV. The prices won't actually be shown in the TV commercials but the advertisement will include a website where the list price will be posted

'Patients deserve to know what a given drug could cost when they're being told about the benefits and risks it may have,' he added in prepared remarks.

'They deserve to know if the drug company has pushed their prices to abusive levels. And they deserve to know this every time they see a drug advertised to them on TV.'

High drug costs have been an ongoing issue in recent years following sudden price increases imposed for some treatments and confusion over how prices are set, with drug companies, insurers and pharmacy benefit managers often pointing fingers at one another.

Most Americans don't pay the full price for prescriptions - one reason drugmakers have opposed disclosing the list prices, arguing that would just confuse the public.

But insurance plans base their copayments on the list price set by drugmakers. And patients with high-deductibles plans or no insurance sometimes pay full price.

President Trump has long promised to bring down drug prices, and in May, his administration released a 'blueprint' with vague proposals for doing so, including exploring listing prices in TV commercials.

Shortly before Azar's speech, the trade group the Pharmaceutical Research and Manufacturers of America (PhRMA) announced plans for television ads that will direct patients to platforms with more information about drug prices, including the expected out-of-pocket costs and options for financial assistance.

The trade group has argued that requiring list prices on ads could confuse patients and perhaps discourage some from seeking needed treatment.

'The (Donald Trump) Administration and Congress have called on our industry to provide cost information in direct-to-consumer advertisements, and our members are voluntarily stepping up to the plate,' said Stephen Ubl, chief executive of PhRMA.

Direct-to-consumer advertising of drugs has been allowed in the U.S. for two decades. Ads are required to list side effects but not prices.

Many details of the proposed rule still must be worked out, including whether it should be expanded to cover radio, print or internet ads. According to the proposal, TV commercials would have to state in legible type the list price set by the manufacturer for all drugs costing more than $35 per month or for a standard course of treatment, such as for an antibiotic.

If the rule is adopted after a 60-day public comment period, Azar's department plans to publicize the names of drugmakers that don't comply and could take legal action against them.

Drugmakers generally can charge as much as the U.S. market will bear because the government doesn't regulate medicine prices, unlike most other developed countries.

List prices have long been closely guarded, and those prices are the starting point for drugmakers' price negotiations with middlemen, such as insurance companies and prescription benefit managers.

According to the government, the list prices for the top 10 prescription medicines advertised on TV range from $535 to $11,000 for a month or course of treatment.

Pfizer's heavily advertised nerve pain drug Lyrica has a monthly list price of $669. Humira, AbbVie's treatment for immune system disorders like rheumatoid arthritis, has a list price of $4,872 per monthly injection. Both have nearly doubled in four years.

Patients for Affordable Drugs, an advocacy group funded by foundations, called PhRMA's website choice 'a transparent attempt to pre-empt full disclosure of list prices in ads,' adding that it doesn't think disclosing list prices will reduce patients' costs.