"The EU is the target of a blackmail," an European Union ambassador voiced his outrage at a meeting this week over the decision made by Turkish President Tayyip Erdogan who opened its border, allowing migrants to mass at Greece's border.

Some envoys conceded, however, that Erdogan has the EU in a bind because its member states cannot agree how to deal with refugees and to avoid a replay of the 2015/16 migration crisis. Some believe the bloc will have to cough up more money for Turkey to go on keeping a lid on arrivals in Europe.

The EU has struggled to respond as thousands of migrants have arrived at Greece's border from Turkey in recent days. Its ties with Ankara are already strained over security and human rights, as well as Turkish hydrocarbon drilling off Cyprus.

Why Turkey opened its border?

Ankara opened the door for migrants last week after a deadly attack on Turkish troops by Syrian government forces in northern Syria. About 34 of Turkish soldiers were killed in the airstrike. President Recep Tayyip Erdogan retaliated by shooting down two Syrian government warplanes last Sunday and one more on Tuesday.

The military clashes in Syria's Idlib region triggered fears of a return to full-scale conflict and has raised concerns of more Syrian migrants heading to the Turkish border. A million people have been displaced since December near Turkey's southern border, causing what the United Nations says may be the worst humanitarian crisis in nine years of war.

Already hosting 3.6 million Syrian refugees, Ankara is determined to prevent any further influx of migrants from Syria. The country opened its western borders on Friday to let migrants reach Europe.

Experts analyze that by allowing migrants into Europe at this point, Turkey wants to draw international attention to the crisis in Idlib, which it fears could send a fresh influx of refugees into Turkey.

The country also considers Brussels to have reneged on the 2016 deal and wants guarantees the EU will continue funding the hosting of refugees on its territory. Under the 2016 deal between Brussels and Ankara, the EU agreed to pay Turkey six billion euros and offered other sweeteners, such as accelerating the lifting of visa restrictions to control the number of migrants heading to Europe via Turkey.

But Erdogan has long complained that the money is slow to come and channeled through aid groups, not Turkey's budget.

Other experts say Turkey also wants the EU to pressure Russia to stop supporting Syrian government troops and agree to a ceasefire since Russia is the mainly strong ally of President Bashar al-Assad's forces and the military escalation in the Idlib region is the reason behind huge migrants influx.

EU dilemma

Compounding the EU's dilemma are internal divisions over how to distribute the burden of caring for refugees and migrants arriving in the 27-nation bloc, although EU officials had promised more cash to Greece to deal with the crisis, during a visit on Tuesday to a Turkish-Greek border crossing that thousands of migrants have been trying to breach.

One senior EU diplomat said the EU had squandered the time since the 2016 deal, brushing the problem under the carpet by paying for refugees and migrants to be kept in Turkey.

Representatives of the Netherlands, Italy, France and Germany were among those who proposed giving more funds to help refugees in Turkey in the hope of appeasing Erdogan. But at the same time, the diplomats believes it's also important not to create the impression of giving in to "blackmail."

However, Turkey's regional foes Greece and Cyprus are particularly worried about mollifying Ankara and demand a tougher EU line.

Several diplomats warned of a repeat of the 2015/16 chaos, which brought more eurosceptic and anti-immigration politicians to the forefront in Europe, saw EU countries slap border controls in what is normally the bloc's zone of free travel, and sowed bitter divisions between member states, damaging EU unity.

These feuds led the EU to eventually outsource migration management to Turkey, despite heavy criticism from rights groups that the scheme aggravates the suffering of already distressed people by leaving them in grim circumstances there.

The EU has not yet discussed numbers for further funding and diplomats said any decision to step up financing could be deferred to the bloc's leaders, due to meet in Brussels on March 26-27.

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(With input from agencies)