People in Wales should still use slotxo the NHS Covid-19 app even if social distancing rules differ from England, the Welsh government has said.
The UK Transport Secretary Grant Shapps said changes to the app could be made, with England set to scrap its lockdown rules on 19 July.
The app also covers Wales, where a similar date has not been given.
The Welsh government said it was working to ensure any changes to the app align with policies in Wales.
The app detects the distance between smartphone users and the length of time spent in close proximity - currently 2m or less and for more than 15 minutes.
It allows people who test positive to anonymously share their test result, triggering alerts for those detected as close contacts in the days before the test.
Those who are alerted then have to self-isolate.
But under plans in England, 1m-plus social distancing rules would be scrapped and the app's sensitivity reduced.
Any changes to Wales' Covid rules will be announced on 15 July.
Covid lockdown rules have often differed in the UK nations during the course of the pandemic, with face masks in shops made mandatory in England before Wales, while Wales entered autumn and winter lockdowns earlier than elsewhere.
On Tuesday, Wales' Health Minister Eluned Morgan said the country was going to have to "learn to live with coronavirus" but the Welsh government would not move to a "political deadline that has been set out artificially" across the border.