New York governor Andrew Cuomo announced Wednesday that he will authorize the medical use of marijuana, making his the 21st U.S. state to do so and one of the biggest. Cuomo, a Democrat who has in the past opposed such a measure, announced a limited pilot program to serve the state of 19.5 million people. "We will establish a program allowing up to 20 hospitals to prescribe medical marijuana," he said, during his annual state of the state speech in Albany. Cuomo argued that research has suggested marijuana, which is widely but illegally used recreationally, can help patients "manage the pain and treatment of cancer and other serious illnesses. "We will monitor the program to evaluate effectiveness in the feasibility of medical marijuana system," he added. Cuomo, 56, who last year spoke his support for decriminalizing the possession of up to 15 grams of the drug, is likely to proceed by decree, after four previous attempts to legalize medical marijuana failed to get traction among the state's lawmakers. The announcement comes as part of a growing movement to relax U.S. laws around marijuana. Including New York, the drug will soon be allowed, to various degrees, for medical reasons in 21 of 50 states and in the capital, Washington. The first state to legalize medical marijuana was California, in 1996. Colorado has gone even further. Since January 1, recreational users older than 21 can legally buy up to 28 grams of cannabis for their own enjoyment regardless of their medical status. The state of Washington took a similar measure, to take effect in the coming months. According to an October 2013 Gallup poll, 58 percent of Americans are now in favor of legalizing marijuana, and 14 states have in recent years decriminalized the possession of small quantities of the drug. Cuomo's announcement comes at an interesting moment in New York politics, with the arrival of Bill de Blasio -- further to the left than the governor -- as the mayor of the state and America's biggest city. Cuomo, meanwhile, has been tapped as a possible presidential candidate in 2016, along with his moderate Republican counterpart in neighboring New Jersey, Chris Christie. New Jersey already authorizes marijuana for medical use within a strict framework.