European foreign ministers appealed to Russia and Turkey to honour the ceasefire in Idlib so that relief can urgently be delivered to refugees in northern Syria.
At an extraordinary meeting in Zagreb, they also agreed that a new donor conference for Syria will be held in Brussels on June 29-30.
Although the member states did not agree on it, some might request in the UN Security Council the establishment of no-fly zone in northern Syria.
Thousands of refugees and migrants are trying to enter the EU after Turkey said its borders with Europe were open. Ankara did so after an escalation of violence in Idlib province, which brought a new wave of Syrian refugees to Turkey's borders.
EU diplomacy chief Josep Borrell told Turkey the first condition was containing the people who believed that the Turkish-Greek border was open. That's a communication issue, people must know the truth. Let's stop this game, he said.
To demonstrate the EU's determination and solidarity with Greece, he said the EU would undertake every measure, in line with European and international law, to protect the integrity of its borders.
Borrell warned about huge difficulties in delivering relief to the civilian victims of a conflict between troops of Syrian President Bashar al-Assad, who is backed by Russia, and rebels helped by Turkey.
You can imagine the logistical difficulties in delivering food, medicines and tents for a million people in the middle of mountains, in the middle of winter, in the middle of war, Borrell said.
In order to help civilians and defuse tensions on the Greek-Turkish border, it will be crucial that a ceasefire signed by presidents Vladimir Putin of Russia and Recep Tayyip Erdogan of Turkey on Thursday be honoured.
We expect the ceasefire to take hold on land and in the air in order to make work easier for humanitarians, Borrell said.
The Croatian EU presidency warned about that too. The extent of the humanitarian crisis is dramatic and it's necessary to ensure access to humanitarian aid, said Croatian Foreign Minister Gordan Grlic Radman.
The EU and Turkey accuse each other of breaching a 2016 agreement under which millions of refugees and migrants were kept in Turkey in exchange for Europe's financial aid. Ankara also accuses Europe of not keeping a vow to liberalise the visa regime and modernise the customs union. Also contentious is Turkey's gas drilling off the Cypriot coast.
Some agreements haven't been implemented, some have been blocked, each side accuses the other. Yet today we hear that the border is open. Please, don't tell people they can go because it's not true, Borrell said, adding that this was the prerequisite for talks on contentious issues.
Grlic Radman said Turkey was not just Erdogan but a big country, an EU accession candidate.
We want a dialogue and to support people, but the country is currently breaching international law, he said, calling on the Turkish authorities to go back to honouring the agreement on refugees.
The aim of the Zagreb meeting was for the EU to agree a common and coordinated response to a possible new migrant tide. During the one in 2015, 1.5 million refugees and migrants arrived in Europe from the Middle East, mostly from Syria. Some member states let them through, while others put up wire fences on internal borders. Populist and anti-migrant parties became popular in nearly every member state.