The bullpen, already an area of strength for the A's, is getting stronger.

Oakland has reached a two-year deal with left-handed reliever Brian Fuentes, a person with knowledge of the deal told The Associated Press on Sunday.

Fuentes is the second highly regarded free-agent reliever the A's have roped in over the past three days. After being passed over by hitters they pursued earlier this winter -- and failing to sign Japanese pitcher Hisashi Iwakuma -- Oakland has money to spend late in the free-agent shopping season.

They're now splurging a bit to build one of the American League's top relief corps.

On Friday, the A's agreed to terms with right-hander Grant Balfour on a two-year, $8.1 million contract with a 2013 club option at $4.5 million, though his deal is pending a physical.

A source told Bay Area News Group that Fuentes will get a two-year deal with a club option for a third year. Fox Sports' Ken Rosenthal reported Fuentes will get more than $5 million per season, and it makes sense that Fuentes would be more costly than Balfour given Fuentes' past experience as a closer.

Fuentes also must take a physical, and assuming all final details get hammered out, it's believed the A's will announce the signings of Balfour and Fuentes on Tuesday or Wednesday.

A's officials don't comment on free agents until they're under contract.

Fuentes, 35, is a four-time All-Star who has averaged 31 saves over the past six seasons with the Colorado Rockies, Los Angeles Angels and Minnesota Twins.

The A's presumably will keep two-time All-Star Andrew Bailey in the closer's role, but Fuentes provides a terrific Plan B if Bailey needs rest or manager Bob Geren wants a left-hander for the ninth.

Adding Fuentes would give the A's eight relievers for what's expected to be a seven-man bullpen: Bailey, Balfour, Fuentes, Michael Wuertz, Craig Breslow, Joey Devine, Jerry Blevins and Brad Ziegler.