The Giants are open to temporarily sharing AT&T Park in San Francisco with the Athletics if their cross-bay rivals decide to build a stadium, Giants president Larry Baer said Thursday.

The Giants are willing to share AT&T Park for a time if the A's build a new stadium ... under one condition. Ezra Shaw/Getty Images

But there is a catch: Any offer would be contingent on the A's not choosing to relocate to San Jose. The Giants' territorial rights extend to the San Jose area, and last year baseball blocked the A's proposal to move south.

"They've got to come up with a long-term plan," Baer told the San Jose Mercury News. "Once that's arrived at, then maybe you'll take a step back and say, 'Is there something we can do to be helpful?' As a neighborly thing."

The A's want out of O.co Coliseum in Oakland, the fourth-oldest park in baseball and the franchise's home since it moved from Kansas City, Mo., in 1968.

Teams sharing a stadium is not without precedent.

In 1975, with Yankee Stadium under renovation, the team called the Mets' Shea Stadium home for that season. In fact, the NFL's Giants also played home games at Shea (then the Jets' home field) in 1975. Giants Stadium in the Meadowlands was finished the following year.