* Opposition says it needs help to unite forces
* Warns of complete chaos without changes to military
* Appeal follows Islamist fighters' attack on warehouses
By Peter Griffiths
LONDON, Dec 12 (Reuters) - Syrian opposition leaders called on Western and Arab allies on Friday to give them funding to reorganise their forces after Islamist fighters seized some of their weapons.
Monzer Akbik, chief of staff in the Syrian National Coalition, said an attack by Islamists on warehouses and headquarters belonging to the opposition's Supreme Military Council near the Turkish border highlighted the need to restructure the rebel forces fighting President Bashar al-Assad.
The United States and Britain suspended non-lethal aid to northern Syria after the attack, which fuelled concerns that supplies could end up in the wrong hands.
The Syrian opposition appealed for money to improve their forces at a meeting in London of the core group of the Friends of Syria, an alliance of 11 countries, including Britain and the United States, which opposes Assad.
"We know that we have a problem, we know that we don't have the organised military institutions that we want. We know of the challenges of the loose organisation of the Free Syrian Army," Akbik told reporters after the meeting.
"We need support, whether it is financial or whether it is equipment. This is the only way to prevent the fragmentations that are going on on the ground."
Asked what would happen if the opposition did not restructure its military, he replied: "Complete chaos. There are many, many groups fighting the regime and fighting each other and fighting al Qaeda. It is a complete mess on the ground."
Under the proposal, the Western-backed opposition would establish a defence ministry and a more formal command structure in an attempt to organise disparate rebel fighters, he added.
Money for proper uniforms, regular wages and food would help to unite the groups fighting Assad, he said.
"The Americans and British are still hesitant, they are not coming in that quickly to support the new project," Akbik said. "We will depend on other sources from Arab countries and perhaps France but not from the Americans and the British."
Elisabeth Guigou, head of France's foreign affairs committee, said the U.S. and British decision to suspend non-lethal aid to the north had been a "surprise", but that for now Paris had no plans to stop its deliveries.
"We have a lot of interest in continuing to support the coalition," she said. "France's diplomatic policy was right to support this opposition from the start," Guigou told a conference of political leaders in Monaco.
"If they don't succeed - and I'm not optimistic - what will we be left with? A regime that uses chemical weapons against its population or jihadis. We want neither one or the other."
In a statement released after the Friends of Syria meeting in London on Friday, the 11 nations condemned the militants' attack on the warehouses.
"The seizing of material assistance for the opposition and Syrian people needs to stop. It does the work of the regime," the statement said. It also reiterated that Assad could have no role in Syria when the fighting ends. (Additional reporting by John Irish in Monaco; Editing by Andrew Roche)