VIENNA - The United States, Italy and Libya's friends and neighbours agreed Monday to arm the war-torn country's fledgling unity government to fight the Islamic State threat.

US Secretary of State John Kerry said a 25-member group had agreed to exempt the Government of National Accord from the UN arms embargo imposed to halt the Libyan conflict.

Along with Italy's Foreign Minister Paolo Gentiloni, Kerry said there are no plans to deploy an international military force in Libya to support the new government. But he said Prime Minister Fayez al-Sarraj had come to Vienna with a request for equipment and training which the international ministers present were ready to support.

"The United States stands ready to provide humanitarian, economic and security support to the new Libyan government on their request," Kerry said.

World powers, he said, will support the GNA's exemption "from the UN arms embargo to acquire those weapons and bullets needed to fight Daesh and other terrorist groups."

The Islamic State group, or Daesh, has seized upon the chaos in Libya to carve out a sizeable enclave around the Mediterranean city of Sirte and to launch attacks beyond. The international community, particularly European powers, are also concerned about a stream of refugees and migrants crossing the Mediterranean from Libya's unsecured coast.

Gentiloni told reporters in Vienna that "the stabilisation of Libya is the key answer to the risks that we have, and to stabilise Libya we need a government."

He hailed Sarraj's decision to create a "presidential guard, which we will support" and a joint operations centre to coordinate a Libyan campaign to defeat the IS menace.

Sarraj thanked the ministers for their support and insisted the Libyans would take the lead in defeating the militants, while seeking weapons and training from abroad.

"The situation in Libya is extremely bad, I'll be very frank, economically, financially and security-wise. It requires the collaboration of all parties," he said.

The three were speaking after a meeting of senior officials from 21 governments and four international organisations, called by Gentiloni and Kerry to address the crisis.

The group included the permanent members of the UN Security Council as well as Libya's neighbours, ensuring that a move to exempt the GNA from the embargo are likely to succeed.

The broader ban on supplying weapons to Libya's other warring factions will remain in place, and even be strengthened, the ministers said.

Libya fell into chaos after a 2011 NATO-backed uprising toppled and killed longtime dictator Moamer Kadhafi. Now, rival militias vie to control the oil-rich country.

Last year, the Islamic State group seized the coastal city of Sirte - Kadhafi's hometown - and transformed it into a training camp for militants.

The unity government was formed in late March after months of negotiation by UN mediators. But while the Government of National Accord has received backing from key institutions like the central bank and the National Oil Corporation, it still faces resistance.

Rival administrations in the east and west of Libya - along with armed militias and a would-be army under a rogue general - still refuse its authority.

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

In their joint statement the ministers placed their support behind the GNA as sole Libyan authority and threatened more economic sanctions against factions that resist its rule.

"We are ready to respond to the Libyan government's requests for training and equipping the Presidential Guard and vetted forces from throughout Libya," they said.

Libya's divisions have once again deepened in recent days, with the GNA and renegade general Khalifa Haftar's forces each announcing their own plans to liberate Sirte. IS is estimated to have around 5,000 fighters in Libya, and it is trying to enlist hundreds more.

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