Sutcliffe will wear the number 14 next season, while Singleton will sport the number 16.
Leeds head coach Brian McDermott is very pleased with the progress that both players have made.
“Both Brad and Liam showed their outstanding potential last season,” he said.
“Brad has been around the first team squad throughout my time here however last season he really grasped his opportunity and this is a reward for those efforts.
“Liam had a great start to 2015 and was unfortunate to suffer a season ending injury. However, his attitude and application since then has been outstanding and he remained a key part of our squad with his positive attitude supporting the squad in the second half of the season.
“He has worked hard with our medical team and I am sure he will come back more determined than ever to succeed.”