KANSAS CITY, Mo. (AP) -Kansas City Chiefs offensive lineman John Welbourn announced his retirement Thursday.

Welbourn, 30, was acquired from Philadelphia in 2004 after coming into the league as a fourth-round draft choice in 1999.

He was hampered by a knee injury during his first year in Kansas City, and was suspended the first four games of 2005 for violating the NFL's policy on performance-enhancing drugs. This season, he would have competed with newly signed Kyle Turley and veterans Jordan Black and Kevin Sampson at right tackle.

``I decided to retire on my own terms rather than somebody else's,'' Welbourn told The Associated Press. ``It was awesome playing in the NFL. I got to play with a lot of great athletes, Will Shields, Willie Roaf, to name a few. I've been playing football for 16 years and it's a little scary to think I won't be playing any more. But at the same time, it's exciting to think I'll be starting a whole new chapter in my life.''

Welbourn, who has nearly completed work on a graduate degree in education, said he planned to enroll in law school. He said he would be filing the paperwork on his retirement with the NFL office.

``I discussed this with the Chiefs a couple of weeks ago,'' said Welbourn, who participated in last month's minicamp but has been unhappy that the Chiefs would not renegotiate terms of his contract.

A Chiefs spokesman said the team had received a fax from Welbourn's representative indicating ``his desire to pursue his studies.'' Kansas City plans to keep him on the active roster for now, in case he changes his mind.

He was primarily a left guard in five years at Philadelphia, where he played in three NFC championship games.

``It's weird thinking I won't be playing football anymore,'' he said. ``Most guys play until they can't play anymore. But I feel good physically and I've been playing well. I'm leaving on a high note.''

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