Per Matt Moore of CBS Sports, Harris' extension with the Nuggets is "very close" and is expected to be finalized before the Oct. 16 deadline.
Harris, the 19th overall pick in 2014, had a breakout campaign last season. The 23-year-old set career highs with 14.9 points, 3.1 rebounds, 2.9 assists, a 50.2 field-goal percentage and a 42.0 three-point percentage in 57 games.
Harris missed 20 of Denver's first 25 games in 2016-17 after suffering a torn groin during a preseason game against the Toronto Raptors.
As he prepares for his fourth NBA season, Harris will make $2.55 million in the final guaranteed year of his rookie contract, per Spotrac. If extension negotiations fall through, he will become a restricted free agent next summer.
The Nuggets, who finished 40-42 last season, have a strong foundation with Harris and Nikola Jokic. Paul Millsap signed with Denver as a free agent this summer to round out the roster.
Signing Harris to an extension would bolster the Nuggets' chances of working their way up the Western Conference standings. They haven't made the playoffs since the 2012-13 season, but they'll have a strong chance of snapping that drought this year.