* M23 rebels disagree with U.N. troops over airport arsenal
* Rebel withdrawal may not be completed until Saturday
* M23 spokesman says some fighters reluctant to quit Goma
* Doubts linger over whether pullout can lead to peace
A planned battlefield withdrawal by rebels in eastern Congo under a deal brokered by regional governments ran into hitches on Friday, including a dispute over abandoned army supplies the insurgents want to take with them.
Leaders of the Tutsi-led M23 rebel movement had agreed to pull out by Saturday from Democratic Republic of Congo's eastern border city of Goma, which they seized on Nov. 20 when they routed government troops backed by United Nations peacekeepers.
Rebel leaders have said that they intend to fight to topple President Joseph Kabila, but they agreed to a call from presidents of the Great Lakes region last weekend for a withdrawal from positions in and around Goma.
As the withdrawal operation showed signs of getting under way, M23 representatives said some of the group's fighters were loath to yield the captured city, and they accused the U.N. peacekeepers of impeding the pullback.
There was disagreement over a store of munitions and equipment that had been abandoned by the government army FARDC at Goma airport. The rebels wanted to take the airport arsenal with them, but the U.N. peacekeeping mission MONUSCO, which had the store under its charge, refused to let them do this.
"This is FARDC ammunition and does not belong to M23 so I don't think we have to hand it over," MONUSCO's spokesman in Kinshasa Madnodje Mounoubai told Reuters by phone.
M23 military chief Colonel Sultani Makenga accused the U.N. peacekeepers of "blocking" M23's withdrawal operations.
"We have a store that has our logistical equipment and now MONUSCO is telling us not to get our equipment. We can't agree to that," he told reporters west of Goma in the town of Sake, from which M23 was also due to withdraw.
The dispute raised questions over whether the rebel pullback from Goma, which is being supervised by military chiefs from neighbouring states including Uganda, would be completed by Saturday morning as announced.
"M23 is going," one of the foreign military observers, Ugandan General Geoffrey Muheesi, earlier told reporters.
A full rebel withdrawal from Goma, which lies on Lake Kivu in sight of the towering Mount Nyiragongo volcano, would signal some progress in international efforts to halt the eight-month-old insurgency in eastern Democratic Republic of Congo.
Goma is an important hub in Congo's eastern borderlands, which have suffered years of recurring conflict stoked by long-standing ethnic and political enmities and fighting over the region's rich resources of gold, tin, tungsten and coltan. The latter is a precious metal used to make mobile phones.
M23 deputy spokesman Amani Kabasha told Reuters that some of the group's young combatants did not understand why they had to surrender a city seized after their offensive.
"We took this town by blood so it is not easy to convince them to leave. They do not understand it," Kabasha said.
In Goma, armed camouflage-clad M23 fighters could still be seen, standing around street corners or in pick-up trucks.
In a sign that Congolese authorities intended to reassert their control over Goma after the rebel withdrawal, 300 policemen, some armed with AK-47s, arrived by ferry at Goma's port on Lake Kivu on Friday and then fanned out around the city.
HUNDREDS INJURED, THOUSANDS DISPLACED
U.N. experts and Congo have accused the government and military of neighbouring Rwanda of supporting, supplying and directing the M23 rebellion, a charge furiously denied by Rwandan President Paul Kagame.
But in the face of the evidence supplied by the U.N. experts, the Rwandan denials have not convinced Western donors, a number of whom have frozen aid to Kigali.
In the latest move, Britain, Rwanda's largest bilateral donor, said on Friday it was withholding 21 million pounds ($34 million) of budget support.
The U.N. Security Council also added two more M23 commanders, Baudoin Ngaruye and Innocent Kaina, to the U.N. Congo sanctions list, U.S. Ambassador to the United Nations, Susan Rice, posted on Twitter on Friday.
"We condemn the actions of the #M23 & those who support them," Rice said.
The Security Council said in a statement in August that U.N. High Commissioner for Human Rights Navi Pillay had named the men among a group of M23 commanders who were linked to past atrocities and presented the gravest risk to civilians.
The medical charity Medecins Sans Frontieres/Doctors Without Borders said the fighting leading to the fall of Goma last week had injured hundreds of people and displaced thousands from their homes. Fighting had also taken place at other locations around Goma, such as Masisi.
President Kabila, who faces resistance from within his own military to a peace with the rebels, has said he is ready to listen to the insurgents' grievances, if they leave Goma. But M23 has expressed scepticism about the offer.
The rebels said initially that they had taken up arms over what they cited as the government's failure to respect a March 23, 2009, peace agreement that envisaged their integration into the army.
They have since broadened the scope of their movement, declaring their aim to "liberate" the entire Central African nation and oust Kabila.
On Thursday, Congo's new head of land forces, Lieutenant-General Francois Olenga, said only war could end the rebellion in the east by the Tutsi-led insurgents.
Humanitarian agencies have said that more than 5 million people have died from conflict, hunger or disease in Congo since 1998.
Rwanda has twice invaded its western neighbour Congo over the past two decades, at one point sparking a conflict dubbed "Africa's World War" that drew in several countries.
It has justified its interventions by arguing that it was forced to act against hostile Rwandan Hutu fighters who fled to Congo after the 1994 Rwandan genocide that saw 800,000 Tutsis and moderate Hutus killed by Hutu soldiers and militia.