Doctors Without Borders warned Tuesday that rising intellectual property rights are blocking the generic production of newer drugs to treat HIV and are keeping them out of reach for developing countries.

The medical aid group said at an international AIDS meeting here that prices of older drugs long used to treat patients have fallen sharply as India and other countries make generics. But newer drugs that are more effective against the AIDS virus are too expensive, costing up to 15 times more.

"It's good news that the price of key HIV drugs continues to fall as more generic companies compete for the market, but the newer medicines are still priced far too high," said Jennifer Cohn, medical director for Doctors Without Borders' access campaign. "We need the newer treatments for people that have exhausted all other options, but patents keep them priced beyond reach."

Patients can be treated with a combination of three or four older drugs, but those who develop resistance to them need the expensive newer medicines.

According to Doctors Without Borders, the governments of Thailand and Jamaica pay $4,760 and $6,570, respectively, a year per patient for the new drug darunavir alone. Paraguay pays $7,782 for etravirine, while Armenia pays $13,213 for raltegravir. In comparison, a cocktail of older generic drugs costs as little as $139 per person a year.

Doctors Without Borders urged the United States and 11 other countries negotiating a Trans-Pacific Partnership not to sign the free-trade pact. It warned that the pact will increase intellectual property rights across Asia and the Americas, expanding monopoly protection for medicines and threatening cheap access to drugs.

It said the World Health Organization's new guidelines, which recommend earlier treatment for adults, means that an additional 9 million people in developing countries will now be eligible for treatment. At the moment, only about 60 percent of those who need the drugs are getting them.

"Scaling up HIV treatment and sustaining people on treatment for life will depend on bringing the price of newer drugs down," said Arax Bozadijan, an HIV pharmacist for Doctors Without Borders.

The Trans-Pacific pact countries account for nearly 40 percent of global GDP and about a third of world trade, and any agreement could significantly impact prices. President Barack Obama's administration has said it hopes to wrap up talks by the end of the year.