NEW YORK (AFP) - New York has signed into law raising the age of criminal responsibility to 18, leaving just one state - North Carolina - where 16 and 17-year-olds are automatically referred to adult criminal courts.

New York Governor Andrew Cuomo signed the reform into law on Monday, the latest in a raft of initiatives seeking to cement his status as one of the leading voices nationwide in progressive Democratic Party politics.

The new measures will be phased in over time, raising the age of juvenile delinquency first to 17 in October 2018, and then raising the age of criminal responsibility to 18 in October 2019.

Those younger than 18 will no longer be held at New York's notorious Rikers Island jail, now earmarked for closure, from Oct 1, 2018.

Instead, they will be referred to juvenile detention under the supervision of children's services.

"A 16 or a 17-year-old who makes a mistake should be treated as a 16 or 17-year old who makes a mistake," Cuomo said.

"They should get help, they should get counseling, they should get a punishment, but not a criminal record that destroys the rest of their lives."

Incarceration of 16 and 17-year-olds falls disproportionately on minority youth - blacks and Hispanics make up 33 per cent of 16- and 17-year-old youth in New York, but 72 per cent of all arrests, Cuomo's office said.

Young people transferred to the adult criminal justice system are 34 per cent more likely to be re-arrested for violent and other crimes than those held in the youth justice system, it added.

State officials estimate that raising the age of criminal responsibility will prevent between 1,500 and 2,400 crimes every five years.

The vast majority of crimes committed by teenagers are non-violent.

Cuomo was joined at the signing by a brother of Kalief Browder, who was held for nearly three years as a teenager without trial and inspired reform efforts, before committing suicide aged 22 in 2015.