WASHINGTON (AP) — Facing a possible strike that could have stranded hundreds of thousands of commuters, Amtrak reached a preliminary deal Friday that apparently heavily favors the railroad's nine unions, who have worked for years without a contract.

The tentative contract includes back pay totaling more than three times what Amtrak was offering and none of the concessions on work rules that Amtrak had been seeking, said Joel Parker, a spokesman for the Transportation Communications International Union and a lead negotiator.

While the month's-end strike was considered unlikely, the mere prospect of it had regional rail services across the Eastern Seaboard scrambling in recent days to put backup plans in place.

"We have averted a possible strike that could have had a crippling effect on the lives of millions of Americans," Amtrak President and CEO Alex Kummant said in a news release.

Details of the agreement will not be released until it is ratified by affected union members in the next several weeks, according to a statement from Amtrak.