Serbia, Bulgaria and Romania have threatened to erect border fences to stem refugee flows if other EU countries close their borders. Leaders have called for a common European response to the crisis.The leaders of Bulgaria, Romania and Serbia huddled together on Saturday in Sofia to develop a common position on the migrant crisis that has upended the Balkan region, ahead of a mini-EU summit on Sunday."The three countries, we are standing ready, if Germany and Austria close their borders, not to allow our countries to become buffer zones. We will be ready to close borders," Bulgarian Prime Minister Boyko Borisov said after meeting with his Serbian and Romanian counterparts.The Balkan leaders agreed to push for a comprehensive European plan at Sunday's summit in Brussels aimed at finding a common cross-border policy to handle nearly 700,000 migrants who have tried to reach Europe so far this year.Speaking after the meeting, Romanian Prime Minister Victor Ponta said the Balkan states were prepared to undertake their obligations and stand in solidarity with Europe."But the responsibility cannot be put with just some countries," Ponta said. "If there are countries which close their borders, or build fences, then we have the right to defend ourselves in a timely manner."Non-EU member Serbia in particular has become a major transit country, as hundreds of thousands of asylum seekers largely from war-torn Afghanistan, Iraq and Syria, pass from Greece and Macedonia on their way to Europe.In recent months, neighboring Hungary has erected fences along its borders with Serbia and Croatia, the latter on October 17.The move has forced refugees to redirect to the small nation of Slovenia, which has struggled to deal with an influx of nearly 58,000 refugees in the past week.The trail of migrants has forced Croatia and Slovenia to at times temporarily close their own borders, leaving refugees fleeing war to now battle rain, mud and cold at Europe's doorstep.Slovenia, a small Alpine nation of 2 million people, has said it may close its border and erect a fence along its frontier with Croatia if the EU does not find a solution. The EU member is also asking for 140 million euros ($155 million) in aid, as well as police and logistical support.Germany, the destination of the majority of migrants, has said it will continue to leave its borders open despite public opinion quickly turning against the prospect of integrating up to 1 million asylum seekers this year.Sunday's mini summit will include non-EU members Macedonia and Serbia, alongside Austria, Bulgaria, Croatia, Germany, Greece, Hungary, Romania and Slovenia.In a sign of how difficult reaching a common policy will be on Sunday, a 16-point plan written up by European Commission President Jean-Claude Juncker and forwarded to participants on Saturday suggested countries in the Balkans not transfer migrants to neighboring countries without first getting agreement.The proposal was immediately shot down by Croatian Prime Minister Zoran Milanovic, who said "whoever wrote this does not understand how things work and must have woken up from a months-long sleep."25 Oct 2015 tjf.j7.sl.pt