"As the fastest growing team sport in the USA, it is the time to have a sanctioned professional competition," USA Rugby chairman Bob Latham said.
"We are very happy to partner with PRO Rugby in taking this step to popularise the game, to inspire Americans to fall in love with rugby, and to show the rugby world what American players can do."
The league's inaugural season will be bankrolled by Doug Schoninger, a New York businessman with a background in finance who is PRO Rugby's chief executive.
"At this point the league's first season is fully funded. It's all coming from me," Schoninger said.
He declined to give a figure for the total cost of the new venture's first season.
Each side would have around 25-30 players per roster while maintaining a quota of five non-North American players per squad.
Rugby has been played in the United States for more than a century and the USA won the gold medal at the 1920 and 1924 Olympics.
Chicago's Soldier Field hosted international matches involving the All Blacks in 2014 and Australia in early September.
- AFP