The United States ambassador to Afghanistan is openly questioning the Afghan government's commitment to fighting corruption after reports a key figure in a massive banking scandal received an early prison release in return for a large campaign donation.

Amb. John Bass' comments Thursday came after local media reports alleged that former Kabul Bank chief executive Khalilullah Ferozi was released into house arrest after a multi-million donation to President Ashraf Ghani's election campaign.

Presidential spokesman Sediq Seddiqi tells The Associated Press those reports are untrue and says Ferozi was transferred into house arrest because of his deteriorating health.

The U.S. comments further strain relations with the Afghan government as a U.S. envoy and the Taliban near a deal to end America's longest war. The talks have excluded Ghani's government.