The New York Yankees and Boston Red Sox escalated their arms race with a flurry of trades Thursday while the San Francisco Giants made the biggest deal of the day, getting Baltimore ace Sidney Ponson.

The AL East-leading Yankees became the latest team to raid the payroll-slashing Cincinnati Reds, acquiring All-Star third baseman Aaron Boone and reliever Gabe White.

New York also traded away third baseman Robin Ventura, while the Red Sox added yet another pitcher, obtaining Jeff Suppan from Pittsburgh. AL Central-leading Kansas City got Tampa Bay’s best reliever, Al Levine, for cash.

In all, there were six trades before baseball’s 3 p.m. deadline for deals without waivers. Now it becomes more tricky to make trades before the Aug. 31 deadline to be eligible for postseason play.

The Giants made a bold move, giving up pitcher Damian Moss, righty prospect Kurt Ainsworth and minor league lefty Ryan Hannaman for Ponson.

Ponson was 14-6 with a 3.77 ERA for Baltimore this season. He was one victory behind AL wins leader Roy Halladay of Toronto.

Ponson goes from a team struggling to reach .500 to a club with a 12-game lead in the NL West.

“Hopefully, I’ll be in the World Series with them this year,” Ponson said.

Ponson turned down a $15 million, three-year contract extension from the Orioles on July 19 and the sides had continued to talk without reaching an agreement. He is eligible for free agency this winter.

“It wasn’t a surprise I was getting traded,” Ponson said. “The Giants are a really good baseball team. I’m looking forward to meeting these guys, and I’m going to do everything in my power to help my new team win it all.”

The Giants had inquired about Montreal pitcher Javier Vazquez before landing Ponson.

The Yankees made a pair of trades with the Reds. They got Boone, whose father was fired three days earlier as Cincinnati’s manager, for prized left-hander Brandon Claussen and cash.

Boone expects to join the Yankees for their game tonight at Oakland. There had been rumors he might get traded to Seattle — where brother Bret plays — or the Dodgers.

“The fact that it’s the Yankees is awesome,” he said.

Boone, 30, was hitting .273 with 18 home runs and a team-high 65 RBIs this season. He also led the Reds with 15 stolen bases.

After getting Boone, the Yankees turned around and sent Ventura to Los Angeles for outfielder Bubba Crosby and right-handed pitcher Scott Proctor.

New York also got White for a player to be named. He was 3-0 with 3.93 ERA in 34 relief appearances, and has been on the disabled list since June 25 because of a strained left groin.

Cincinnati fired manager Bob Boone and general manager Jim Bowden Monday. Since then, the Reds traded closer Scott Williamson to Boston and productive outfielder Jose Guillen to Oakland.

“They’ve had a change of direction,” Yankees general manager Brian Cashman said. “All of baseball reacted to that. When the Reds’ situation changed, it created a whole new market.”

While the first-place Yankees have recently added relievers Armando Benitez, Jesse Orosco and White, the Red Sox have traded for pitchers Byung-Hyun Kim, Scott Sauerbeck, Williamson and Suppan.

In a reworking of a July 22 trade, Pittsburgh sent Suppan, right-hander Brandon Lyon and minor league pitcher Anatascio Martinez to Boston for infield prospect Freddy Sanchez, minor league left-hander Mike Gonzalez and cash.

Suppan spent most of his career in the AL before signing with Pittsburgh, going 48-57 with the Red Sox and Royals. He is 10-7 with a 3.57 ERA this season, with three complete games and two shutouts during his current five-game winning streak.

“When I left (Pittsburgh), I told him I’d probably see him in a few weeks,” Sauerbeck said. “Now it’s true.”

Toronto general manager J.P. Ricciardi said it seemed only teams with money were able to make trades.

“It sounds like it’s a repeat of the ’50s where the Yankees used to go to the Kansas City A’s and take their players and give them money so they could survive,” Ricciardi said.