CHICAGO - Major League Baseball owners on Thursday unanimously approved television contracts with Fox and TBS that run through 2013 and are worth more than $3 billion.

Under the deals, which begin next season, the World Series, All-Star games and Saturday afternoon regular-season telecasts remain on Fox. Turner Broadcasting System will show all first-round playoff games, and the two networks will share the NL and AL championship series, alternating leagues each year.

Fox will have the ALCS next year, while TBS will have the NLCS. The start of the World Series also will be pushed back three days next year, from Saturday to Tuesday.

The owners also voted during the two-hour meeting to extend the Major League constitution through 2012. They approved an amendment that clarifies the votes needed to amend and extend the constitution. It takes a simple majority to extend the constitution; amending it requires the approval of three-quarters of the owners.

“This is one of the earliest and quickest meetings we’ve ever had,” commissioner Bud Selig said.

After the meeting, Selig said opening the 2008 season in China remains a possibility. China is the world’s biggest country with more than 1.3 billion people, and MLB hopes the sport will become as popular there as it is in other Asian nations. However, a suitable ballpark must be constructed.

MLB recently announced plans to open an office in China within the next month. San Diego Padres chairman John Moores and chief executive officer Sandy Alderson have already traveled to China to study the feasibility of holding a season opener there.

MLB already has had regular-season games in Japan twice. The New York Yankees and Tampa Bay Devil Rays opened the 2004 season there, and the New York Mets and Chicago Cubs played in Tokyo Dome in 2000.

If baseball opens the 2008 season in China, it would come three months before the Beijing Games — the last Olympics where baseball and softball are to be played. The International Olympic Committee took both sports off the program for the 2012 Games in London.

“We’ve talked about that,” Selig said about holding the 2008 opener in China. “I certainly want to open in as many countries as possible. ... China is the next great horizon. The greatest potential in this sport is international.”

Slideshow   The Week in Sports Pictures The Giants on top of the football world, getting ready for the London Olympics and more. more photos

On Tuesday, the Boston Red Sox bid $51.1 million for the right to sign Japanese pitcher Daisuke Matsuzaka. With a contract added to the fee, he stands to become the most expensive pitcher in the game — and one of the priciest players at any position.

But Selig, who has in the past tried to preach fiscal restraint to owners, didn’t seem concerned that the blockbuster deal would set a tone for the free-agent market.

“It’s sort of a unique situation,” he said. “We haven’t started yet. Time will tell.”

Selig also had little to say about the general managers’ latest attempts to add instant replay — an idea he has opposed for years.

The GMs, meeting this week in Naples, Fla., asked a committee that deals with umpires to come up with recommendations on replay. Many GMs would favor replay on fair and foul calls as well as disputed home runs, but past discussions have gone nowhere — in part because they know Selig opposes it.

“I have great respect for the general managers,” Selig said. “They’re certainly entitled to look at things, and I’ll be happy to discuss anything they’d like to discuss.”