WASHINGTON — President Bush on Wednesday appointed an emergency board to help Amtrak settle its dispute with nine labor unions and avoid a crippling strike during the busy holiday season.

The intervention had been expected, though unions had been making preparations for a strike just in case.

About 10,000 Amtrak workers have been working under outdated contracts for nearly eight years. However, the Railway Labor Act does not allow them to strike until federal officials determine that mediation has been unsuccessful.

The National Mediation Board released the parties from mediation Nov. 1, which triggered a 30-day cooling-off period. If not for Bush's order, the unions would have been free to strike after the cooling-off period expires Friday night.

Under the order, the five-member presidential emergency board will have 30 days to recommend a resolution, starting at 12:01 a.m. Saturday. Amtrak and union officials have said they expect an extension to be granted because of the holidays.

Wednesday's order did not name the members of the board.

After the emergency board completes its work, the law requires another 30-day cooling-off period. At the end of that, if Amtrak or the unions reject the board's recommendations, the workers can strike. However, Congress also can intervene to compel the parties to accept certain terms.

Amtrak has never had a strike in its 36-year history. If one were to occur, it would bring all Amtrak operations to a standstill, since even non-striking unions would honor picket lines, said Amtrak spokesman Cliff Black.

The major sticking points in the negotiations have been back pay and proposed work rule changes.