Porter told The Associated Press on Monday morning that Suns general manager Steve Kerr broke the news to him at a Sunday night meeting.
"I'm going to wait a few days to gather my thoughts before I say anything," Porter said.
Assistant coach Alvin Gentry will replace Porter, although the Suns have not yet made an announcement concerning their coaching situation.
Porter's dismissal was first reported by The Arizona Republic on its Web site Sunday.
Porter was in the first year of a three-year, $6 million deal to replace Mike D'Antoni, who left after four highly successful seasons to coach the New York Knicks.
D'Antoni is a coach who lets his players run and shoot, and maybe play defense once in a while. It was Kerr's insistence on emphasizing defense that led, in large part, to D'Antoni's departure.
Porter wanted a defense-oriented team in the tough mold of the Detroit Pistons.
It was a bad fit.
Gentry, extremely popular with Suns players, has been a coach in the NBA for 20 years, including interim head coaching stints with Miami and Detroit. He was coach of the Los Angeles Clippers from 2000 to 2003.
"I think Alvin is a great players' coach," Suns forward/center Amare Stoudemire said after Sunday's All-Star game in Phoenix. "He gets along with his players well. Of course, he'll have a great game plan from a basketball standpoint. I think it will be somewhat up-tempo."
Asked if the coaching change was needed, Stoudemire said, "Only time can tell."
"I think Terry Porter definitely put a lot of hard work in here to try to get us on the right track," he said, "and I'm pretty sure Alvin's going to do the same."
Phoenix (28-23) lost five of eight going into the All-Star break and trails Utah by one game for the eighth and final playoff spot in the West.
Gentry was the only holdover from D'Antoni's staff in Phoenix. His hiring as assistant coach in 2004 coincided with the arrival of Steve Nash and the subsequent ultra up-tempo offense that propelled the Suns to 54 wins or more in each of the past four seasons.
The decision to replace Porter came in a series of meetings between owner Robert Sarver and Kerr reviewing the entire basketball operation. The two also are considering trading Stoudemire in a move designed to clear salary-cap space.
It marks the second time Porter has been fired as an NBA coach. He was let go by the Milwaukee Bucks in 2005 after two seasons.
Porter, who played in the NBA for 17 seasons, was an assistant with the Pistons when he was hired by the Suns, and the intention was for him to bring the Pistons' defense-oriented, slower playing style with him.
That plan was jettisoned after it became apparent the Suns were not suited to the slowdown game.
The promotion of Gentry means the Suns will be even more committed to a fast-paced style.
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