Welsh Secretary Cheryl Gillan says she has spoken to the home secretary about the threatened closure of the passport office in Newport.
Ms Gillan said she had impressed on Theresa May the impact of the office's closure on the city.
She condemned the staff's union for leaking details of the move.
First Minister Carwyn Jones is writing to David Cameron about the closure and feared 300 job losses, claiming the assembly government had no warning.
Ms Gillan said she had been talking to ministerial colleagues at the Home Office since she was made aware of the proposals for the Newport office of the Identity and Passport Service (IPS).
She said the discussions are due to resume next week and it was important to remember "the consultation process has not yet begun and no final decision has yet been reached".
She added: "I condemn the way news of the consultation was prematurely leaked on a Friday afternoon before staff could be properly informed by management - it was not the right way for staff and their families to be treated."
The Public and Commercial Services Union (PCS), which revealed the proposals, said the office's closure move would have a "devastating" impact on Newport.
The office, which opened in 1967, is one of seven regional UK passport centres but the only one believed to be closing.
Carwyn Jones said the UK government had "completely lost the plot on this one".
He said there was no economic argument to close the Wales passport office which also serves people in the west of England.
He told BBC Wales: "It's unbelievable to think that out of seven passport offices there should be nothing in Wales but passport offices in England, Scotland and Northern Ireland.
He said the announcement had come "completely out of the blue" and that "the way that this has been handled, frankly, is unbelievable".
Welsh Labour MEP Derek Vaughan, a former PCS trade union official, described the closure move as a "dangerous precedent for things to come".
He said: "Wales will now be the only European country without a single, proper passport office.
"People from Wales will now be forced to travel all the way to either London or Liverpool to get the level of face-to-face service that they deserve. This is clearly unacceptable."
PCS is holding a meeting on Monday to organise its campaign.
The IPS said its system currently has too much capacity which could only be resolved by closing a regional passport centre.
It said analysis had found that closing Newport would result in the greatest reduction of spare capacity at the lowest cost to the taxpayer.
Welsh Liberal Democrat leader Kirsty Williams AM said: "To suggest that every passport office should remain open except for the only one serving south Wales and south west England is at best high handed and will leave millions of people with an inferior service to the rest of the UK, as well as threatening hundreds of jobs.
"Of course, all public agencies must seek to achieve best value for money in very difficult times but this must be done sensitively with the aim of providing a good service across the UK."