PHOENIX — Arizona Diamondbacks All-Star right-hander Dan Haren has agreed to terms on a four-year, $44.75 million contract that runs through the 2012 season with a club option for 2013.

Haren, acquired in an offseason trade with the Oakland Athletics, is 12-5 with a 2.75 ERA, fourth-best in the National League. He is fourth in the NL in strikeouts with 142 and leads the league in strikeout-to-walk ratio at 5.92.

"I knew I'd like it here but I didn't know I'd like it this much," Haren said at a news conference at Chase Field today. "A lot of these guys are going to be around for a while and I'll be one of them. I just couldn't be happier."

The 27-year-old Haren is part of a potent 1-2 Arizona pitching punch with staff ace Brandon Webb, who also has had talks with the Diamondbacks on a new deal.

Haren's new deal includes $31.5 million more than he would have made in his old contract, which ran through 2009 with a team option for 2010. If the club picks up the option for 2013, the new contract would total $56.75 million.

The contract pays him $7.5 million in 2009, $8.25 million in 2010, and $12.75 million in 2011 and 2012. The deal includes a $3.5 buyout if the team doesn't pick up the option.