EU officials discussing migration on Tuesday expressed concerns that a threat by Turkey to send its troops into northeast Syria might provoke a new wave of refugees to Europe.
Interior ministers meeting in Luxembourg noted that the so-called eastern Mediterranean route from Turkey to Greece has once again become the main channel for asylum-seekers reaching Europe.
"For Greece, the spike of the increase of the flows between May and today is an increase of 240 percent. You can imagine the scale of the challenge," said Greece's alternate minister for migration, Giorgios Koumoutsakos.
Greece, Bulgaria and Cyprus delivered a joint statement at the meeting calling attention to the eastern Mediterranean route.
"Geopolitical factors, including conflicts in the broader area particularly in Syria, entail that we will most likely see a continuation of this alarming trend in the short to medium term,” the statement said.
Turkey has said its preparations for a military operation in northern Syria against Kurdish fighters it views as "terrorists" is complete, and it has deployed armoured vehicles to the border.
Its path into northeast Syria was cleared by US President Donald Trump on Monday ordering American troops out of that zone because of Turkey's intentions.
Officials in the EU said that if Turkey does invade part of Syria, many of the four million refugees Turkey is hosting - most of them Syrians - may decide to head to Europe to avoid being forcibly pushed back into their unstable homeland.
Read more: Syria's Kurds abandoned to a perfect storm of Turkish aggression and US isolationism
"I hope there won't be an operation," Luxembourg's foreign minister, Jean Asselborn, told reporters.
"But imagine that you're a refugee in Turkey, you're Syrian - the risk exists that you might be transported one day... into northeast Syria. That's a factor that could generate a wave towards Europe," he said.
Asked about that scenario in a media conference, the EU's commissioner for migration, Dimitris Avramopoulos, said "the European Union remains committed to the unity, sovereignty and territorial integrity of the Syrian state".
The EU, he added, urged "the cessation of hostilities, the protection of civilians and unhindered, safe and sustainable humanitarian access to all of Syria".
The EU Security Commissioner Julian King was asked about Trump's criticism that European countries had "refused" US demands to take back their citizens who had fought for the Islamic State group and were now being held in northeast Syria.
He replied that the issue was "a matter for national authorities, and they guard that jealously".
He noted that EU agencies stood ready to help gather and process evidence of alleged crimes committed by the ex-fighters should they ever be repatriated to face trial.
The Syrian conflict, which has left hundreds of thousands dead mostly as a result of regime bombardment of civilian areas, began with the brutal suppression of pro-democracy demonstrations by the Assad regime.
Meanwhile, the top Republican in Congress warned on Monday that an abrupt pullback of US troops from Turkey's border with Syria would only benefit Russia, Iran and President Bashar al-Assad's government in Damascus.
Senate Majority Leader Mitch McConnell became the most senior lawmaker in Donald Trump's party to oppose the president's announced decision to withdraw from certain positions in northern Syria, one that effectively abandons the Kurds, one of Washington's main allies in the war against Islamic State group militants.
"A precipitous withdrawal of US forces from Syria would only benefit Russia, Iran, and the Assad regime," McConnell said in a statement, joining a broad bipartisan outcry on Capitol Hill.
"And it would increase the risk that ISIS and other terrorist groups regroup," he said, using an acronym for the Islamic State group.
McConnell is a vital Trump ally in Congress and has the power to decide which bills get brought to the Senate floor for a vote.
In a veiled warning to the White House, he recalled how a veto-proof bipartisan "supermajority" in the Senate voted on a measure last January that criticized Trump's order to withdraw all 2,000 American troops from Syria.
Trump's full withdrawal did not proceed, but it shocked allies and led to the resignation of Pentagon chief Jim Mattis.
"The conditions that produced that bipartisan vote still exist today," McConnell said, noting the Islamic State group and Al-Qaeda "remain dangerous forces in Syria" and that the country's ongoing civil war poses significant security risks.
"I urge the president to exercise American leadership to keep together our multinational coalition to defeat ISIS and prevent significant conflict" between Turkey and US counter-terrorism partners in Syria.
A furious Senator Lindsey Graham, another Trump ally, said earlier Monday that he would introduce a resolution "opposing and asking for reversal of this decision" to pull back from parts of northern Syria if Trump goes ahead.
Graham then added that he and Senate Democrat Chris Van Hollen would introduce a sanctions measure against Turkey if its forces invade Syria "and will call for their suspension from NATO if they attack Kurdish forces."
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