An English hospital is refusing to accept patients from Wales except in emergencies and maternity cases.
The decision by the Countess of Chester NHS Foundation Trust, which is just miles from the border with North Wales, is likely to affect thousands living in Flintshire.
The hospital stopped accepting non-emergency admissions for people from Wales on Monday.
It comes amid a row over payments to the hospital by Betsi Cadwaladr University Health Board, which coordinates NHS services in North Wales.
The hospital’s chief executive, Susan Gilby, told the BBC it was a “difficult decision” over “unresolved funding issues”.
"Unfortunately, the trust is currently unable to accept any new elective work relating to patients living in Wales,” she said.
"We will of course honour any existing appointments so there will be no disruption for patients already waiting. This is a difficult decision that has been taken with great reluctance."
Last year, the trust’s chairman said 20 per cent off the hospital’s patients live in Wales and that costs for treatment were “up to £4m each year”.
Rates for operations by NHS England are slightly higher than those in Wales, meaning the Countess of Chester is paid less for treatment on people living in Flintshire compared to those in England.
Ms Gilby said negotiations to resolve the issue were continuing between the trust and the health board.
But a Welsh government spokesperson told the BBC the trust’s decision to limit patient access on financial grounds was “not acceptable”.
"Along with NHS Wales representatives, Welsh Government has agreed a process of engagement with Department of Health and Social Care officials and representatives from the English NHS to discuss cross-border payment arrangements," he said.
"In the context of ongoing engagement, any actions taken by English providers to limit access for Welsh patients on financial grounds are unacceptable and not in the spirit of reaching a cross-border agreement with English NHS representatives."
