Turkish President Recep Tayyip Erdogan sought more European support on Monday over the war in Syria and for hosting millions of Syrian refugees, but was told he must first stop encouraging migrants to cross into Greece. Erdogan flew to Brussels for talks with the European Union and NATO after tension rose over the fate of tens of thousands of migrants trying to enter EU-member Greece since Ankara said last month it would no longer try to keep them on its soil. Turkey hosts about 3.6 million refugees from Syria under a deal it agreed with the EU in 2016 in return for billions of euros in aid for the refugees. But it has become frustrated with what it regards as too little European support over the war in Syria, where its troops are facing off against Russian-backed regime forces and have suffered growing casualties. "The crisis stemming from Syria, with its security and humanitarian aspects, is threatening our region and even all of Europe," Erdogan said after arriving for with the EU and NATO. "No European country has the luxury to remain indifferent." "We expect concrete support from all our allies in the fight that Turkey has been carrying out alone ... NATO is in a critical period during which it needs to clearly show support." The EU has little to offer in terms of military support in Syria, where it has condemned Turkeys engagement. The 27-nation bloc, in which most members are also Ankaras NATO allies, has dangled the promise of further aid - but under conditions. "The events at the Greek-Turkish border clearly point to politically motivated pressure on the EUs external border," the head of the European Commission, Ursula von der Leyen, said before talks with Erdogan. "Finding a solution to this situation will require relieving the pressure that is put on the border," she added. Precondition The EU is determined to avoid any repeat of 2015 and 2016, when more than 1 million people, mostly from the Middle East, reached its shores via Turkey and Greece. That flow was largely halted by the 2016 deal with Turkey, which the EU hopes to salvage. The EU says it has so far paid about half of a promised 6 billion euros to help Turkey finance housing, schools and medical centers for the refugees stranded on its territory. "A precondition for any additional EU help should be to stop all support to illegal border crossings and move people away from the border," a German conservative member of the European Parliament, Manfred Weber, said. The 2016 accord had also envisaged the EU taking in thousands of Syrian refugees directly from camps in Turkey, rewarding Turks with visa-free travel to the bloc and faster progress in EU membership talks. But ties between the two soured following a botched coup against Erdogan in July 2016. The EU criticized the scale of Erdogans post-coup crackdown on critics and has effectively frozen Turkeys long-stalled bid to join the bloc. NATO head Jens Stoltenberg told a meeting with Erdogan that the alliance has already invested more than $5 billion in Turkey, including in military bases and radar sites.