The extension is for five years and $65 milliion and will go into effect next season, the source said.
If Aldridge achieves certain hard-to-reach incentives, his contract could ultimately be worth as much as $70 million.
The deal comes after a summer of angst between the Blazers and their two young potential free agents -- Aldridge and Brandon Roy. The Blazers, after some verbal sparring, reached an agreement with Roy on a five-year, $80 million dollar max contract. Aldridge was searching for a similar contract from the Blazers but after several months of negotiation settled on a deal worth roughly $15 million less.
General manager Kevin Pritchard drafted both players in 2006 and they have become the centerpieces of the Blazers' youthful, up-and-coming team.
Teams have until Oct. 31 to reach extension agreements with players taken in the 2006 draft. To date, only Andrea Bargnani, Aldridge and Roy have received extensions. Several other key players from that draft, including Rajon Rondo, Rudy Gay and Tyrus Thomas, are still negotiating with their respective teams. If players and teams do not reach an agreement on an extension by Oct. 31, the players will become restricted free agents in the summer of 2010.
Chad Ford is a senior NBA writer for ESPN.com.