Guard Rubio is widely considered as one of the most promising players in the NBA, with Minnesota looking to gain extra security, instead of allowing him to become a restricted free agent next summer.
"I feel optimistic. Knowing Ricky the person, he wants to be here," Newton told reporters, according to Fox Sports.
"We just have to deal with his agent. We have Ricky for two more years, and we're in constant contact with his agent. There are some things that we agree on, some things we don't agree on.
"If we can get something worked out, fine. If not... he's under contract."
The new NBA season is due to commence on October 28, with the San Antonio Spurs taking on the Dallas Mavericks.