It was easy to see what Dr Rexhepi, a medical man turned city administrator, was talking about. If the head of Mitrovica's unofficial, Albanian-created municipal government cannot even heat his own office above freezing point, why should anyone listen to him?
A few hundred yards away, across the bridge dividing Kosovo's second city, local Serbs were angry. For the first time since Nato-led peacekeepers entered Kosovo in the summer, a British Warrior armoured vehicle had appeared on their side of the Ibar river. Its commander explained that he was on attachment to the French element of KFOR, which is headquartered in Mitrovica and has "solved" the problem of ethnic tensions by closing the bridge over the Ibar river to keep the two communities apart.
Without an interpreter, however, he could not calm the crowd, which was circulating wild rumours of an imminent British attack and threatening to kill the crew if they did not move on. Senior French officers, Italian carabinieri and a red-and-white "Coca Cola" vehicle of the United Nations police were all drawn in by the confrontation. From their headquarters in Mitrovica's tallest building, next to the bridge, officials of the United Nations Mission in Kosovo (Unmik) would have been able to see what was happening, but the incident, like many in Kosovo, dragged on noisily, messily and without resolution.
For Dr Rexhepi the lesson was obvious. "Unmik must impose its authority here," he said, and it was clear that he meant the whole of Kosovo, not just Mitrovica. "If the UN people simply administer this place on paper and try to act as mediators, they encourage extremists on both sides to make more demands. Unmik is very anxious to have a success in Kosovo, but all we can see is dithering."
In the rest of Kosovo the problem is different, but the UN is again criticised. Serbs who sought to live peacefully among their Albanian neighbours have almost all been driven out, either to Serbia or into a handful of heavily guarded enclaves, in what bears all the signs of a co-ordinated campaign: the officially disbanded but still well-armed Kosovo Liberation Army convinces few with its denials of responsibility.
The UN police, barely half the promised strength of 3,100, have been powerless to prevent reverse ethnic cleansing. Their commitment is also in question - according to one aid worker, an Albanian policemen he knew found himself trailing his foreign superiors from one coffee bar to another.
"Many of the international police see no point in risking their skin," he said. "All they want to do is bank their bonuses and get home in one piece."
The euphoria which greeted Nato peacekeepers when they entered Kosovo six months ago today is evaporating as the UN struggles with the myriad problems left behind by the Serbian destruction. It is behind schedule in many if not most areas, from registering the population and their cars to establishing a tax system and preparing for eventual elections, but its failure to deal with law and order undermines everything. Apart from disrupting attempts to set up a smooth-running administration, rampant crime is alienating the population.
UN officials complain that all the talk of billions of dollars for the reconstruction of Kosovo after the war has come to nothing, and that Unmik is constantly short of funds. Its critics retort that two-thirds of its running costs go on paying the generous salaries of its international bureaucrats. A classic "UN economy", familiar from other trouble spots such as Cambodia and Bosnia, is developing in Kosovo. Anyone with the resources to open a restaurant or coffee bar can make a fortune, while newly appointed customs officials at the border with Macedonia earn 300 Deutschmarks (pounds 100) a month, and even that was not paid for the first four months.
"Unmik is creating a base for corruption in Kosovo with such disparities," complained Baton Haxhiu, editor of Koha Ditore, the most prominent Albanian- language newspaper.
Mr Haxhiu said that Dr Kouchner, a former French health minister and founder of Medecins sans Frontieres, had been reduced to making constant "moralistic appeals" to Albanians to show ethnic tolerance and support Unmik. "But who will protect us if we do? Why do we have crime in Kosovo? Because we don't have identity cards, the power and water are off several hours a day, cars have no licence plates and nobody controls the traffic. Nobody knows who is who in Kosovo, and it is an El Dorado for criminal gangs from Albania."
Apart from smuggling drugs, arms and cigarettes into Kosovo, Albanian gangsters have taken to kidnapping young women for prostitution in western Europe. Mr Haxhiu said one had been snatched from outside the Grand Hotel in the heart of Pristina last week, while four UN policemen looked on.
Even if the UN can curb the lawlessness, however, it faces a contradiction at the heart of its mission. Officially Kosovo remains under Serbian sovereignty, but everything Unmik does, as one official admitted, works against Belgrade's control. "There was an outcry when we made the Deutschmark the working currency, for example," said the official, "but we couldn't reintroduce a banking system with a dead currency like the Serbian dinar."
Since nearly every Kosovar Albanian insists independence is the only option - the timing is the sole matter of dispute - UN efforts to maintain links with the remaining Serbs further erode support among the majority population. "Unmik must stop trying to appease the Serbs," complained Dr Rexhepi. "They are only a fraction of the population, and they must accept that they are no longer privileged."
The Mitrovica administrator would have been horrified to hear the UN official who admitted that attempts to keep Pristina University open to all groups had failed. Since it was now entirely Albanian, Unmik was considering whether to turn the mining and metallurgical faculty, on the Serbian side of Mitrovica, into a separate university for Serbs. "Apartheid?" responded the official. "Call it that if you want to."