The US State Department says it hopes to reach a deal quickly with France to compensate Jews transported to Nazi concentration camps during World War II on French trains.
Spokeswoman Jen Psaki confirmed Washington and Paris are discussing "compensation for victims of deportations by rail from France to Nazi labour and death camps as well as for victims' families."
And she called on "all concerned to avoid actions that undermine the ongoing compensation talks".
"It is our mutual aim to conclude these talks as quickly as possible," Psaki added in a statement on Wednesday.
But she criticised state lawmakers in Maryland, some of whom are seeking to take their own action against the French rail firm SNCF, a move she said had "begun to pose a serious obstacle to achieving this goal".
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During the occupation of France by Germany, the Nazi regime deported almost 76,000 Jews to concentration camps in French freight cars between 1942 and 1944.
Only around 3000 survived.
The French rail firm has protested that it had no choice as it was simple a "cog in the Nazi extermination machine" and that any eventual compensation should be paid by the French government.
But the sensitive, decades-long issue of SNCF's role in the deportations threatens a bid for a contract worth up to $US3 billion ($A3.21 billion) between the rail company and the US state of Maryland.
Maryland lawmakers had demanded that SNCF compensate the victims before being allowed to join the bidding process for local projects and introduced bills to that effect.
But those measures never made it to a vote during the 2014 legislative period that ended at midnight on Monday, according to sources in both state chambers.
This means that SNCF, via its subsidiary Keolis America, will be able to bid on the 25-kilometre public-private light rail project between now and this northern summer.
During emotional hearings in March in Annapolis, Maryland, Holocaust survivors and their families had demanded they be compensated for their ordeal.
"The current American-French dialogue, in our view, represents the best means of reaching an agreement that will meet the concerns expressed by lawmakers in these states," Psaki said.
SNCF, in eyeing the contract, is part of a consortium comprising French firms Alstom and Vinci. A winning bid is expected to be picked by the end of the year or in early 2015.
