Rebels in Libya are struggling to hold their front line after Col Muammar Gaddafi's forces recaptured several towns in the east of the country.
The rebels have now lost the key oil port of Ras Lanuf and the nearby town of Bin Jawad. However, reports say the fighting is continuing in the area.
In the west, the rebel-held town of Misrata is still coming under attack from pro-Gaddafi troops, reports say.
US President Barack Obama earlier said he did not rule out arming the rebels.
France and the US say they are sending envoys to the rebel-held city of Benghazi in the east to liaise with the interim administration there.
And British Foreign Secretary William Hague said a UK diplomat met Libyan rebel leaders in Benghazi earlier this week.
The UK has also made moves to expel five Libyan diplomats based in London, Mr Hague told MPs on Wednesday.
Allied frictionMr Obama told reporters on Tuesday that Col Gaddafi had been greatly weakened by the coalition air strikes and would ultimately step down.
UK Prime Minister David Cameron told MPs at Prime Minister's Questions on Wednesday that the RAF had flown 24 sorties over Libya on Tuesday night.
These had destroyed artillery and an armoured vehicle near the strategic city of Sirte, which is Col Gaddafi's birthplace.
It lies on Libya's northern coast roughly half way between the capital Tripoli and Benghazi.
As fighting intensified on Wednesday, the BBC's Ben Brown in Ajdabiya said he had seen the rebels sending reinforcements to the front line, including four Katyusha rocket systems.
On Tuesday, US Secretary of State Hillary Clinton and Mr Hague both suggested the UN resolution authorising international action in Libya could also permit the supply of weapons.
This message was reinforced by Mr Cameron in his comments to MPs on Wednesday, in which he said that as the UN ceasefire was clearly being breached it was right to keep up pressure from the air, while not ruling out the option of arming the rebels.
"UN [Security Council Resolution] 1973 allows all necessary measures to protect civilians and civilian-populated areas, and our view is this would not necessarily rule out the provision of assistance to those protecting civilians in certain circumstances," he said.
"We do not rule it out, but we have not taken the decision to do so."
But Russian Foreign Minister Sergei Lavrov denied UN Security Resolution 1973 gave a mandate to arm the rebels.
"The Nato Secretary General Fogh Rasmussen declared that the operation in Libya was being staged to protect the population and not to arm it - and here, we completely agree with the Nato secretary general," he said.
In a separate development, an international conference on Libya in London has agreed to set up a contact group involving Arab governments to co-ordinate help for a post-Gaddafi Libya.
Several thousand people have been killed and thousands wounded since the uprising against Col Gaddafi's rule began more than six weeks ago.
