First Minister Mark Drakeford has defended the slower rollout of the vaccination programme in Wales - saying the Pfizer vaccine could not be used all at once.
The Welsh Government has faced criticism in the past week for vaccinating fewer people in proportion to its population than the other home nations.
Statistically, Wales is behind the other nations of the UK in delivering the first dose of the vaccine per 100,000.
As of last week, 3,215 had received it in Wales, compared to 3,514 in Scotland, 4,005 in England and 4,828 in Northern Ireland.
Mr Drakeford dismissed the statistics as "very marginal differences", and went on to explain that supplies of the Pfizer vaccine had to last until the beginning of February and would not be used all at once.
"There will be no point and certainly it will be logistically very damaging to try to use all of that in the first week and then to have all our vaccinators standing around with nothing to do with for another month," he told BBC Radio 4's Today programme.
"The sensible thing to do is to use the vaccine you've got over the period that you've got it for so that your system can absorb it, they can go on working, that you don't have people standing around with nothing to do.
"We will vaccinate all four priority groups by the middle of February, alongside everywhere else in the UK."
Mr Drakeford said Wales was "on track" to vaccinate the top four priority groups by the middle of February.
"The thing that limits us at the moment is supply and we're using every bit of the vaccine that we are getting," he said.
"We know that that supply will be ramping up rapidly over the coming weeks and we are ready to use all the supply that we are getting in Wales and on track to deliver vaccination to the priority groups."
In a video posted online, the First Minister said he wanted to "be completely clear" and that "no one is holding back vaccines".
"All our health boards are receiving doses of Pfizer as quickly as quickly as they can use it," he added.
The British Medical Association has expressed concerns about the Welsh Government's vaccine roll-out strategy.
Dr David Bailey, Chair of the BMA in Wales said: “For the First Minister to say that there is ‘no point’ in using all the supplies in a week to ensure vaccinators aren’t standing around with nothing to do is truly bewildering.
“Frontline staff are risking their lives to help others - the priority must be to get the second dose administered to those who have received the first, and to accelerate first doses for all remaining vaccinations to ensure maximum protection for staff and patients. We are asking Welsh Government to stop sitting on supplies and get on with it.”
The First Minister told Sky News around 150,000 people would have been vaccinated in Wales by the end of Monday.
"We're getting more supplies of vaccine this week, particularly the Oxford vaccine, and we'll be able to use all of that," Mr Drakeford said.
"There's a long way to go with vaccination - we're going to be doing this for months and months, not just for weeks.
"At the moment, the thing that is limiting us is just volume of supply, we could vaccinate more people than we've got vaccine.
"But we also know that that, too, is going to increase rapidly over the coming weeks."
"One of those batches has not come through the testing process and we will get it next week, we're told, instead," Mr Drakeford added.
"When you're trying to do everything on a massive scale and at such speed there are going to be moments where not everything goes according to plan.
"But we are assured we will get that supply in exchange for this week next week, and we will be able to use it all then."
Welsh Conservative shadow health minister Andrew RT Davies said: "Whether intended or not, this outburst of honesty from the First Minister tells the Welsh people all they need to know.
"The Welsh Labour Government is failing to deliver its vaccine programme.
"His shocking doubling-down on his decision to delay deployment of Pfizer vaccine supplies is dangerous, and makes no clinical sense whatsoever.
"We need to get these vaccinations into people's arms ASAP. Lives and livelihoods across Wales are at stake."
Conservative former Welsh Secretary Stephen Crabb said: "Some astonishing comments this morning from Labour's First Minister in Wales defending his go-slow vaccination strategy.
"Over-80s in Wales desperate to know when their vaccinations will be starting."
Plaid Cymru leader Adam Price has also criticised the Welsh Government's handling of the vaccine rollout saying "saving lives is more important than saving stocks."
Mr Price has urged Mr Drakeford to vaccinate people "as fast as possible" instead of a "slow and steady" approach.
Plaid's health spokesman Rhun ap Iorwerth said: "Wales appears now to be dramatically behind England in terms of vaccine rollout, so to see the First Minister being relaxed about the slow pace of the vaccine rollout here is very, very frustrating.
"The most recent data from both NHS England and Public Health Wales demonstrates that Wales is lagging way behind.
"Comparing Wales and England isn't always useful - for various reasons, we're ahead on some things, and England ahead on others - it's swings and roundabouts. But where it's a four-nations programme, we need to know it's a level playing field.
"Welsh Government must give an update on vaccines made available for Wales - of each type - plus numbers vaccinated in Wales compared to England, using the different types of vaccine, and on the projected supply of vaccines in the weeks to come. Why are we rationing here?
"Transparency is crucial at this stage so that progress can be measured, and that both governments can be held accountable and questioned on progress where needed."
Dr Andrew Goodall, chief executive of NHS Wales, said the health service in Wales had been legally obliged to hold onto all supplies of the Pfizer vaccine to give the second dose within the then three-week requirement.
"The access to the Pfizer vaccine has been the same across the UK, particularly with the Medicines and Healthcare Regulatory Agency guidance which actually changed around the second dose on January 4," he said.
"It was in line with the legal advice and the MHRA handling arrangements.
"The second dose needed to be retained up until the point that we were authorised to proceed with all the residual numbers of those vaccines, and that was a consistent standard that was in place for the whole of the UK.
"The vaccination activity has been increasing at pace and scale.
"We have a target, as with the rest of the UK to ensure that we're able to make the first four cohorts by mid-February, and at the moment we expect that our activity profiles will allow us to ensure that those targets are met by mid-February."