GENEVA (Reuters) - The U.N. refugee agency appealed to Serbian authorities on Friday to provide access to tens of thousands of displaced people inside the troubled province of Kosovo in line with a peace plan agreed in Moscow this week. The Geneva-based UNHCR reported that the refugee flow from the Serb province into north Albania stopped abruptly on Tuesday and said it suspected the border was sealed by Serbian forces.“The border is no longer crossable but we haven‘t been told by anybody officially,“ spokesman Kris Janowski told a briefing. „We are certainly worried. We virtually have no access and we know very little about what is going on there.“ On a visit to Moscow, Yugoslav President Slobodan Milosevic issued a joint statement with President Boris Yeltsin on Tuesday committing himself to a political solution. Western diplomats said Milosevic had only a few days to start proving that his commitments to open up a dialogue and allow outsiders into the crisis zone were sincere. But many suspect he is unwilling to make any fundamental change of strategy in Kosovo where the conflict has fanned fears of a wider Balkan war. Up to 13,000 refugees have poured into northern Albania over the last two weeks fleeing months of violence as Serbian police continued their crackdown on pro-independence Kosovar gunmen. Since the flow into northern Albania stopped, Janowski said the exodus into neighbouring Montenegro appears to be picking up. Inside Kosovo, the UNHCR says 45,000 ethnic Albanians have been uprooted since the latest flare-up of violence in the undeclared war between Serbian security forces and the separatist Kosovo Liberation Army (KLA) of ethnic Albanians. Hundreds of people have died since Serbian forces launched a campaign earlier this year to crush the KLA in villages along the Albanian border in Kosovo where 90 percent of the two million residents are ethnic Albanians.