MILWAUKEE — First baseman Prince Fielder and the Milwaukee Brewers reached a preliminary agreement today on an $18 million, two-year contract.

The agreement is subject to a physical, Brewers general manager Doug Melvin said.

Melvin declined to discuss the contract's value.

"There's things you have to do to get to that point to finalize deals," Melvin said. "We won't have anything tonight, but there's a good possibility we could have something tomorrow."

Milwaukee renewed Fielder's contract last year for $670,000, and Fielder was eligible for arbitration for the first time. He asked for $8 million and the Brewers offered $6 million when figures were exchanged Tuesday.

He can become a free agent after the 2011 season.

"We'd know his salary for the next two years and still have him the following year when he goes back into the arbitration pool," Melvin said. "He's still our player, but there's an undefined salary for the third year."

In 2007, Fielder became the youngest player to hit 50 home runs, and he batted .288 with 119 RBIs. The 24-year-old hit .276 with 34 homers and 102 RBIs last year as Milwaukee reached the postseason for the first time since 1982.

AP Baseball Writer Ronald Blum in New York contributed to this report.