American Express (Amex) has blocked support by Curve within days after the UK startup announced the feature.

Curve allows consolidation of all debit and credit cards into one card, and very recently added support for Amex cards in its Beta. It would have allowed cardholders to transact even at retailers that usually do not accept Amex.

The fintech has been trialling with Amex in closed Beta since November last year. However, just days after the addition of the support, Curve issued a notice to customers saying that Amex had terminated their merchant services agreement.

Curve faced a similar challenge in 2016, when it launched Beta and added Amex cards acceptance along with Visa and Mastercard. The card giant then asked the fintech to remove support for its cards.

After seeking a new merchant account, Curve signed a merchant services agreement with Amex in March 2018, and re-launched support for a small group of its customers in November.

During the test phase, about 500 Curve users spent more than £1m on their Amex card by paying with Curve.

The fintech went on with a full launch on 28 January this year, but received a notification of agreement termination, with immediate effect, from Amex on 29 January.

Commenting on the move, Curve said: “Amex breached their contract with Curve, failed to give appropriate notice, breached PSR regulations, and demonstrated clear anti-competitive and anti-innovation behaviour.”

Curve added that Amex raised concerns over customer experience but did not provide any additional details.