WASHINGTON (Reuters) - Washington Nationals manager Jim Riggleman resigned abruptly after the team's 1-0 win over the Seattle Mariners on Thursday, saying he was upset by a lack of discussion over his future at the team.

Riggleman said he had sought a conversation with Nationals general manager Mike Rizzo about the team picking up an option to retain him for the 2012 season.

"I want to make one thing very clear -- I wanted a conversation about it," Riggleman said on the Major League Baseball website (www.mlb.com).

"I didn't say, 'Pick up my option, or else.' I said, 'I think it's worthy of a conversation when we get to Chicago,' and Mike (Rizzo) said, 'Well, we're not going to do that.'"

Rizzo painted a different version of the conversation.

"Jim told me pre-game today if we wouldn't pick up his option, then he wouldn't get on the team bus," Rizzo said.

"I told him I thought he was doing a great job as the manager of this club. I'm the guy who hired him as the manager of this club.

"We have discussed his option being picked up several times during the season. I felt the time wasn't right for me to pick up the option."

The Nationals had just completed a three-game sweep of the Mariners and have won 11 of their past 12 games to improve to 38-37 on the season.

"You've got to feel there's a commitment to you, and I just didn't feel that way," Riggleman said.

"I just felt that it's worthy of a conversation.

"I just felt that I know I'm not (late Hall of Fame manager) Casey Stengel, but I do feel like I know what I'm doing, and it's not a situation where I felt like I should continue on with such a short leash where every little hill and valley is life and death."

(Reporting by Mike Mouat in Windsor, Ontario. Editing by Ian Ransom)