One of the two parcel bombs intercepted last week after being sent from Yemen was defused 17 minutes before it was due to explode, France's Interior Minister Brice Hortefeux has said.
The two bombs were being sent via air freight to the US but were intercepted in Dubai and the UK and defused.
A White House spokesman said the 17 minutes claim could not be confirmed.
Mr Hortefeux did not say which of the two bombs he was referring to or reveal his source.
"There were parcel bombs from Yemen heading for the United States, and I can tell you, for example, that one of these parcels was disarmed 17 minutes before the planned explosion," he said.
Mr Hortefeux was speaking to France-2 television.
White House spokesman Robert Gibbs said the question of when the bombs were to go off was still being investigated and there was no evidence to confirm Mr Hortefeux's statement.
An official in the United Arab Emirates told Associated Press news agency that if Mr Hortefeux was referring to the Dubai bomb then he was "not correct".
A British official also told AP that the UK bomb was still under investigation and the possible timing of its detonation had not been determined.
Neither official could be named because they were not authorised to speak on the investigations, AP said.
Security forces in Yemen are hunting for al-Qaeda in the Arabian Peninsula's suspected bomb maker, Ibrahim al-Asiri, in connection with the two devices. He is also suspected of being behind last year's failed 25 December attempt to bomb a US airliner and other attacks.
The bombs were found after a tip-off from Saudi authorities and were pulled off US-bound planes in England and Dubai.
They were made of a difficult-to-detect explosive called PETN, and concealed within printer cartridges inside larger packages.
German officials have said the bombs contained 300-400g of PETN, more than enough to cause a large explosion.
Both bombs were wired to circuit boards from mobile phones but did not contain the SIM cards needed to receive calls, US officials have said. This indicates the phones were to be used as timers.
US officials also said packages intercepted in September that were linked to al-Qaeda in the Arabian Peninsula may have been a dry run for last week's bombs, as the bomb makers could trace the route and timings of the packages delivery on the freight companies' websites.
A number of Western countries have suspended air freight from Yemen and tightened security of air cargo in light of last week's events.