The US will listen to all sides in Libya but will only recognise the democratically elected House of Representatives, US ambassador to Libya Deborah Jones said this morning.

She insisted though this did not mean the US would agree with every decision taken by the House of Representatives such as a recent blanket labelling of Misurata militias as terrorist groups.

She was speaking in Malta at the US ambassador's residence in Attard, a month after the US temporarily shut down its embassy in Tripoli and transferred operations here.

Asked about developments that saw Islamic-leaning militants take over Tripoli and reconstituting the previous parliament, Ms Jones said the land grab may have been a way of gaining leverage before any talks can start.

"There remains a preponderance of Libyans who want to work for a united country and I would not underestimate the value of legitimacy in the eyes of the international community that has recognized the elected House of representatives," she said.

Ms Jones said the UN security council would in the coming days discuss a resolution asking all parties in Libya to agree on a ceasefire but it will also include some form of sanctions against those who breached international laws and destroyed civilian infrastructure such as the airport.

She said the decision to leave Libya was one of the saddest decisions in her diplomatic career. The US embassy compound had only just been opened a month before but had to be shut down after heavy fighting broke out in the vicinity.

Ms Jones said the US military provided air cover as the long convoy of embassy vehicles made it to Tunisia by road.

Ms Jones said the recent airstrikes conducted by an outside force in Tripoli against militant targets failed to achieve their objective and insisted such unilateral interventions were wrong.

The two sorties by fighter jets were reportedly conducted by the United Arab Emirates using basis in Egypt.

"The US believes that any actions that exacerbate damage to the basic infrastructure that hits Libyans in their everyday life is wrong," she said, adding that US intervention in Iraq - against Islamic State extremists - was different because it was done transparently and in cooperation with the international community.