No decision has been made on whether to deploy UK Apache helicopters to Libya, the government has said, contradicting claims by a French minister.
French Defence Minister Gerard Longuet said on Monday that Britain would follow France in using attack helicopters against Col Gaddafi.
But UK defence minister Nick Harvey contradicted Mr Longuet's claim.
His clarification came after Labour tabled an urgent question about the reported "escalation" of the mission.
Mr Longuet told reporters at an EU meeting on Monday: "The British, who have assets similar to ours, will also commit. The sooner the better is what the British think."
But Mr Harvey told the Commons on Tuesday: "My understanding is that the French have indeed take a decision to deploy their attack helicopters in Libya.
"I state again for the avoidance of all doubt: no such decision has been taken by the United Kingdom.
"It is an option we are considering and there is absolutely no sense in which it is true to say that we have kept Parliament in the dark about a decision."
He insisted the use of helicopters would not represent an escalation of the Nato mission in Libya but only a "tactical shift" to improve the ability to strike moving targets more precisely.
Later, US officials appeared to confirm an Apache deployment by the UK despite the government's denials.
"This additional contribution by the British, of course, is an important effort to strengthen the capability of the coalition, and we certainly welcome it," a White House spokesman said.
BBC defence correspondent Caroline Wyatt said some military sources do regard the use of French attack helicopters - and perhaps UK Apache attack helicopters at a future stage - as an escalation of the campaign, and an extremely potent and effective weapon.
Our correspondent said military commanders say Apaches have proved their worth in Afghanistan against insurgents, who fear the arrival of the helicopters as much as - if not more - than fast jets.
This is because the helicopters' weapons can be used to deliberately target individuals such as snipers - even in built-up areas.
However, experts say that although the helicopters are able to identity targets quickly, they are more vulnerable than the strike aircraft.
One Nato source told the BBC that while Nato had not pressed the French to offer attack helicopters, the alliance was delighted that they were being sent, as they marked a "significant stepping up" of capabilities in Libya.
If used, the UK's Apache attack helicopters could deploy from HMS Ocean, the Royal Navy's largest warship, our correspondent added.