* Hague says no deadline for UK involvement in Libya
* Urges rebel leaders to flesh out transition blueprint
By Christina Fincher
LONDON, June 5 (Reuters) - Libyan rebels need to flesh out their plans for post-Gaddafi rule and convince members of the current Libyan administration that they could work together, British Foreign Secretary William Hague said on Sunday.
Speaking on his return from rebel-held Benghazi, Hague said he was confident that the rebels' desire for democracy was genuine but conceded their blueprint was "embryonic".
"We're encouraging the National Transitional Council to put more flesh on their proposed transition -- to lay out in more detail this coming week what would happen on the day that Gaddafi went -- who would be running what, how would a new government be formed in Tripoli?" Hague told the BBC.
He said lessons had been learned from the lawlessness that followed the overthrow of Saddam Hussein in Iraq and the plan put forward by the Transitional Council envisaged technocratic members of Muammar Gaddafi's government working alongside opposition members.
"They now need to publicise that more effectively, to be able to convince members of the current regime that that is something that would work," Hague said.
Hague travelled to Benghazi on Saturday and held discussions with the National Transitional Council, which Britain recognises as the legitimate representative of the Libyan people.
Now in its fourth month, the Libyan conflict is deadlocked, with rebels unable to break out of their strongholds and advance towards Tripoli, where Gaddafi appears to be entrenched.
Hague said the NATO campaign against forces loyal to Gaddafi was intensifying. But he rejected suggestions Britain had strayed from the U.N. mandate to protect civilians.
"It is better to stay strictly within the United Nations resolutions, keeping all the legal, moral and widespread international support that comes from that, than it is to seek a short-cut to the end of this," Hague said.
"We will continue in that vein, intensifying what we're doing -- the Apache helicopters are an example of that. But this is different from mission creep."
British and French attack helicopters struck inside Libya for the first time on Saturday -- a development Harriet Harman, opposition Labour's deputy leader, called "a major escalation" that increased the risks to British troops.
Some politicians have called for a fresh vote in parliament on Britain's role in Libya.
Hague acknowledged it was not possible to say when the conflict would end.
"We're not going to set a deadline," he said. "It could be days or weeks or months. It is worth doing." (Reporting by Christina Fincher; Editing by David Cowell)
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