Communications Minister Ed Vaizey is to announce that the Government is to press ahead with a switchover to digital radio - but will shy away from setting a date.
He will say the FM signal should be switched off when "the weight of public opinion" dictates.
A provisional target date of 2015 had been identified by the outgoing Labour government but Mr Vaizey will say a decision will not be made until half of all radio listening is via digital sources.
For many drivers it will mean the prospect of buying new radios or using conversion kits as digital radios are not often fitted as standard.
Figures from radio industry audience body Rajar show that around 24 per cent is currently via digital.
Mr Vaizey is to publish a Digital Radio Action Plan encouraging listeners to make the switch. This will involve building DAB coverage, which only covers about 90 per cent of the population, and a cost-benefit analysis of the changeover.
Earlier this week the BBC Trust rejected proposals to close down the digital station 6 Music which had been put forward by BBC director general Mark Thompson.