Patients from Powys face longer waits for surgery compared to those waiting from across the border, warns a hospital in England.
More than 7,000 patients from Wales were treated at Shrewsbury last year
Last year nearly 1,000 more Welsh patients - the majority from Powys - were treated at the Royal Shrewsbury Hospital than were planned.
And unless the new Powys Local Health Board provides enough funds to cover all patient treatment then waiting times for patients will increase.
Talks are continuing between the hospital and Powys Local Health Board about financing treatment for patients.
The Royal Shrewsbury Hospital treated 7,600 patients from Wales in the last 12 months compared to a planned figure of 6,700.
Services at the hospital include a renal unit as well as vascular, eye, ear, neck and general surgery.
A hospital report says negotiations with primary care trusts in Shropshire will ensure that waiting list targets will be met for the majority of English patients.
However, the hospital warns it is unlikely that Welsh trusts will provide sufficient funding to maintain existing waiting time targets.
Waiting time targets in England incorporated in the hospital's plan are nine months for non-emergency surgery, and a maximum of 17 weeks wait for an out-patient appointment.
But no standard into the planning has been incorporated for patients in Wales.
The hospital said the service and financial framework had been agreed with the Shropshire health trust which will ensure that waiting time targets for this year will be delivered.
Spokesman for Royal Shrewsbury NHS Trust, Phil Hipkiss said: "For Powys this is not the case.
"Although negotiations are continuing it would appear that, due to financial considerations, activity levels will have to reduce compared with last year.
"This may result in increases in both the total numbers waiting and the waiting times for routine cases for Powys and patients."
He stressed that negotiations with Powys Local Health Board were continuing and a deal would be finalised in the next month.
Montgomeryshire Community Health Council's Chief Officer John Howard said that one in nine people treated at the hospital came from Powys.
He added that Powys Local Health Board faces funding problems because it has inherited a debt of £4m from Dyfed Powys Health Authority which it replaced as a commissioning body at the start of this month.
"The problem in Powys is that we don't have a district general hospital here so we have to buy in services from hospitals such as those in Shrewsbury and Aberystwyth," he said.
"Unfortunately the board is not given money to pay for this two-tier system.
"It will have to look at, for example, cataract operations being provided in Powys in future rather than people going out of county to have this done."
A Powys Local Health Board spokesman said: "Discussions are ongoing between Powys Local Health Board and its various service providers, including the Royal Shrewsbury Hospital, to secure service agreements that will improve waiting times for treatment for Powys residents."