Rep. Jim Kolbe, a leading proponent of free trade and the only openly gay Republican in Congress, announced Wednesday that he will not seek a 12th term next year, and cited Washington's increasingly partisan atmosphere as one reason he's leaving.

"The mood on Capitol Hill is not a pleasant one," Kolbe said in a conference call. "There's a divisiveness that I think we haven't seen in a long time and I worry about that. I like to think that I've been a moderating influence on that."

Kolbe, 63, said in a statement that he wants to find "new avenues of service" and spend more time in Arizona. He said in the conference call that he didn't have specific plans, but has always wanted to teach or do consulting work.

Because of self-imposed Republican term limits, Kolbe will lose the chairmanship of the powerful House Appropriations subcommittee on foreign operations and export financing in 2006, something he said factored into his decision to retire.

Kolbe often disagrees with his party on gay rights issues. He reluctantly acknowledged in 1996 that he is gay, beating to the punch a national gay magazine that planned to do an article on him after he voted against federal recognition of same-sex marriages.

Kolbe is a strong proponent of free trade and a guest-worker program for immigrants. He is popular in his Tucson-area district, receiving 61 percent of the vote in 2004.

He was first elected to Congress in 1984, when he defeated Democratic Rep. Jim McNulty.