DALLAS, DEC. 9 -- Although the timetable still is uncertain, the methodical wheels of major league baseball turned ever so slightly toward expansion today with a series of vague, yet significant announcements.

The most concrete one was that major league owners have decided to merge the American and National Leagues' expansion committees and have asked them to begin discussions on pushing the mechanics of expansion forward.

"The train has left the station," Commissioner Peter Ueberroth said. "The owners were never asked, 'Do you favor expansion?' But I never heard a single owner say they were against it. There were lots of discussions, and the feeling was that we move forward. . . . There was not one word about specific cities because there are still a couple of hurdles."

The hurdles could be large ones. Ueberroth and the presidents of both leagues emphasized there would be no expansion until baseball gets a new basic agreement and television contract. Both expire in December 1989, although Ueberroth would like to begin renegotiation of each next year.

However, negotiations of those contracts historically have gone months past the expiration date and, if that happened again, expansion teams might not begin play before the 1992 season.

That appears to be an even greater possibility in the player-owner negotiations for this new basic agreement. With owners having effectively shackled free agency, they now publicly admit to wanting the arbitration procedure changed.

But the players see the arbitration procedure as their last bit of control and, as one player representative said recently, "There's so much bad feeling that if there's a strike in 1989, it may be the longest ever. Don't you think they want to break us like the football owners broke their union?"

Ueberroth previously has said that baseball's revenues will decrease in the new television contract, although he backed off those statements this week.

Regardless, the issues of labor and television are so critical that league officials said they're not even close to asking candidate cities to re-apply for admission. As negative as all that sounds, the momentum for expansion does appear to be alive for the first time in a decade.

"The responsible thing to do is clear up these two complex, important issues first," National League President A. Bartlett Giamatti said. "No one thinks it would be wise to add a wing to a house until the foundation is secure . . . That isn't to say the next bulletin won't come until December 1989, but we won't contemplate anything much before that. These are major management issues, and they require careful, complex hard work."

Representatives from Washington and the D.C. Baseball Commission handed out brochures and key rings this week to remind baseball of the District's continuing interest and, after today's announcement, they reacted positively. "I expected it in 1989 or '90," said Jim Dalrymple, general manager of RFK Stadium. "There was no expansion talk for a long time, and now it's very much on their minds. I think Giamatti is going to be a driving force for it."

Ueberroth has said he favors adding six teams, two to the American League and four to the National League. That would mean the formation of four eight-team divisions, and both league presidents appeared to be generally in favor of such a concept.

If that is the case, there also appears to be widespread support for inter-league play. For instance, Philadelphia Phillies owner Bill Giles said he wouldn't favor expansion until inter-league play was considered.

Giamatti said another factor was the status of the San Francisco Giants, who are searching for a new home after their downtown stadium proposal was defeated by voters last month. Giants owner Bob Lurie has said he'd like to remain in the Bay Area (perhaps San Jose), but Giamatti said, "We're mindful to protect the rights of existing franchises to relocate."

Ueberroth will meet with a group led by Sen. Timothy Wirth (D-Colo.) next week in Washington, but said he'd tell them the same thing he told the media today.

"I'm going to sit down with them and be as frank as I can," he said. "If we go to hypotheticals, we tend to mislead people. I didn't hear any discussion of not going forward today."