Uruguay's President Jose Mujica on Tuesday signed off on regulations for his country's landmark legalization of its marijuana market.

The small South American country in December became the first in the world to announce that it would regulate the market for cannabis and its derivatives, a bold move by authorities frustrated with losing resources to fighting drug trafficking.

The new rules state that the officially sanctioned marijuana will have a 15 percent concentration of tetrahydrocannabinol (THC) — the plant's main psychoactive ingredient — and come in five varieties.

Buyers must be 18 or older, residents of Uruguay, and must register with authorities.

Officials said customers can buy up to 10 grams of marijuana a week at a price of 20 to 22 pesos (about $0.90) per gram.

Mujica, 78, is a leftist former guerrilla and medical doctor who leaves office this year.

Heavily criticized by the United Nations' International Narcotics Control Board (INCB), Uruguay's marijuana experiment is being closely followed by countries eager to find an alternative to the expensive and violent "war on drugs" spearheaded by the United States.