Major powers including the United States met in the Austrian capital on Monday to discuss the expanding presence of the Islamic State jihadist group in conflict-ridden Libya, just across the Mediterranean from Europe.

IS has taken advantage of the chaos left by the toppling and death of longtime dictator Moamer Kadhafi in 2011, which led to rival militias vying for control of the oil-rich country.

A recently formed unity government backed by the international community has been slowly asserting its authority in Tripoli but it still faces a rival administration in the east.

In a bid to stabilise the country, the fledgling regime has drawn up a list of requests for Western partners to assist its forces with arms, training and intelligence.

The Vienna conference is being co-chaired by the United States and Italy, Libya's former colonial ruler which has faced a major influx of migrants from the North African nation braving the perilous sea voyage.

More than 20 top diplomats are set to attend the meeting, due to start at 1200 GMT.

"We have a lot of work to do," said US Secretary of State John Kerry during a brief press appearance with his Jordanian counterpart Nasser Judeh at Vienna's plush Bristol Hotel, as the pair held talks ahead of the official gathering.

The conference is also expected to focus on the flow of illegal immigrants from Libya to Europe, after a damning report from the British parliament suggested last week that an EU naval mission to combat people trafficking was "failing".

The Government of National Accord headed by businessman Fayez al-Sarraj has won international support as well as backing from key institutions like the central bank and the National Oil Corporation. 

But it has failed to get the endorsement of the elected parliament and its ally Khalifa Haftar, a self-declared army chief who has launched a crusade against Islamist fighters across the country.

A rival Tripoli-based government has also refused to recognise the GNA.

Amid the chaos, the Islamic State group has carved itself a bastion in Libya where it overran last year the Mediterranean coastal city of Sirte, Kadhafi's hometown, transforming it into a training camp for militants.

Europe fears the jihadists, who have in recent weeks made new advances, will use Sirte's port and airport as a springboard to launch attacks on the continent.

The concerns have struck a chord with Washington, where officials and diplomats say plans are being drawn up to loosen a ban on arms exports to Libya imposed five years ago by the United Nations.

A senior US administration official told AFP that Libya's international partners were willing to help, if the GNA presented a "detailed and coherent list" of what it needs to fight IS.

"There is a very healthy desire inside of Libya to rid themselves of (IS), and I think that is something we should be supporting and responding to," the official said.

But diplomats have warned that the GNA may struggle to come with a concrete request for help.

Libya's divisions have once again deepened in recent days, with the GNA and Haftar forces each announcing plans to fight IS and "liberate" Sirte.

"This is a mistake. It must be prevented... we can no longer accept this division," said Nicola Latorre, chairman of the defence committee of the Italian Senate and an IS expert.

Claudia Gazzini, senior analyst on Libya for the International Crisis Group, has also warned that the race for Sirte is pushing any hope of a political solution in Libya further away.

IS is estimated to have around 5,000 fighters in Libya, and it is trying to enlist hundreds more.

This month the jihadists launched suicide attacks on key checkpoints in government-held territory along the Mediterranean coast.

The move allowed them to build a defensive line along part of the coastal highway that links the east of Libya where Haftar is based with Tripoli in the west. (AFP)