LONDON - Britain's financial watchdog said on Wednesday it has extended temporary licences for only a "small number" of cryptocurrency firms ahead of an April 1 cut-off date to prove sufficient money laundering controls.

Crypto firms must have a licence showing they have sufficient checks and controls to stop money laundering or terrorist financing.

"We have concluded our assessments, and the temporary registration regime will close on 1 April, for all but for a small number of firms where it is strictly necessary to continue to have temporary registration," the Financial Conduct Authority said on its website.

"This is necessary where a firm may be pursuing an appeal or may have particular winding-down circumstances."

Placing the firms on its list with temporary registrations does not mean they have been assessed as fit and proper, the watchdog said.

Firms still operating under a temporary licence on Wednesday include relatively large players such as Copper Technologies and Revolut.

David Raw, an FCA policy official, said this month that 90% of crypto firms seeking approval for their anti-money laundering controls have either withdrawn their applications or been refused because they could not meet the standards.

"It won't be the case that you suddenly have to cease trading," Raw had said regarding firms whose licence applications could not be fully processed by the April 1 deadline.

(Reporting by Huw Jones, editing by Ed Osmond)