The U.S. company XpressWest has announced it is terminating its cooperation with China Railway International in building a high-speed rail between Las Vegas and Los Angeles.

Chief executive of Las Vegas-based XpressWest, Tony Marnell, says that his company's ambitions outpace China Railway's ability to move the project forward timely and efficiently.

China Railway says XpressWest is irresponsible in making such a decision while bilateral talks are still on-going.

A China Railway manager says the unilateral announcement also violated the cooperation framework agreement signed by the two sides, which stipulates that one side should not release related information without the approval by the other.

The two companies reached a deal to build the high-speed rail link in September.

The past few months have been a bumpy ride for bilateral negotiations.

China Railway management have said that XpressWest had kept adding new demands in the talks, some of which were unacceptable to the Chinese firm.