German chancellor Angela Merkel has backed giving Turkey a multibillion-euro aid package to cope with refugees, giving impetus to a provisional EU deal with Ankara that aims to slow the flow of migrants to the EU.

The ambitious draft deal agreed in Ankara between the European Commission and Recep Tayyip Erdogan, Turkey’s president, turns on a host of sweeteners Ankara has sought for years, including visa-free access for Turks visiting Europe.

However, Turkey’s most demanding terms await explicit approval from EU member states, some of which remain wary of the high political and financial price that Mr Erdogan is insisting upon.

In a show of goodwill on Thursday night, a summit of EU leaders “welcomed” the migration “action plan”, noted efforts to fast track visa liberalisation, and pledged to “re-energise” Turkey’s EU membership talks.

Commission officials briefed EU ambassadors on Thursday on the Turkish requirements for completing the terms of the action plan, including €3bn in fresh funds; unblocking about five chapters in Turkey’s EU membership negotiations; and visa-free access for 75m Turks to the Schengen border-free area from as soon as 2016.

EU officials insist no promises were made to Mr Erdogan beyond an original offer of about €500m in assistance from the EU’s budget. But Ms Merkel made clear that the question of the larger €3bn in aid “did play a role” in summit deliberations.

“In the future we have to be stronger in burden sharing if we think of the fact that they [Turkey] have been virtually left alone in the past,” she said. “If we say Turkey has indeed spent €7bn over the past few years, then in turn, that would mean the EU also shoulders a comparable sum.”

Mr Erdogan also made clear that Turkey would expect to be included in an EU “safe list”, which would make it easier to reject Turkish asylum seekers. He also expects the EU to hold a joint summit with Turkey, or invite him to speak to a summit of EU leaders.

In return, Turkey pledges strengthen its border controls — including greater co-operation with Greece, which has seen a massive influx of refugees from the region.

In exchange for visa privileges, Turkey would complete a “readmission” deal to take back third-country asylum seekers that entered the EU from Turkish territory. Turkey would eventually also give the 2m Syrian refugees a legal route to make a living in Turkey, reducing the incentives to attempt to enter Europe.

EU leaders have viewed Mr Erdogan with increasing disdain in recent years amid evidence of his creeping authoritarianism.

But since Europe’s migration crisis overwhelmed the continent, the bloc has scrambled to entice him, knowing his support is essential to stem the flood of asylum seekers coming to Europe.

Ms Merkel will visit Ankara on Sunday, days before a crucial November 1 parliamentary election in which Mr Erdogan’s Justice and Development party is fighting to regain its majority. She said her trip would be aimed at setting a more precise timetable for Turkey to implement the action plan.

Turkey hosts about 2m Syrian refugees and of the approximately 350,000 asylum seekers that have attempted to enter the EU since January, just 50,000 were stopped at the Turkish border.

While Europe has suddenly become far more forthcoming in its relations with Mr Erdogan, senior ministers admit that Ankara’s terms, including visa liberalisation, may ultimately be impossible for them to deliver. François Hollande, the French president, stressed any new visa rights or headway in Turkey’s membership talks would be contingent on Ankara meeting conditions.

“We insisted that this visa liberalisation will happen on an extremely precise and monitored basis . . . I insisted on this so that there is no misunderstanding or ambiguity,” he said.

Diplomats were surprised by the €3bn funding demanded by Turkey. The commission initially suggested about €250m in extra EU funding, topped up to about €500m by EU member states. Britain is particularly concerned about any funding that would stretch the EU’s common budget beyond its annual limits.

Several member states — led by Cyprus, which is in a decades-long dispute with Ankara over its occupation of half the island — are also opposed to linking any migration deal to an acceleration of Turkey’s stalled EU membership talks. Although the EU has agreed in principle to open talks on monetary policy, Turkey is demanding that additional chapters are also unfrozen on justice, fundamental rights, energy and education.

The existing “road map” with the EU foresees visa liberalisation as soon as 2017 but it is full of difficult political and technical conditions, including the effective recognition of Cyprus. While Brussels insists the conditions would not be watered down, it wants the process accelerated to 2016.

Before the migration crisis, France and Germany opposed such liberalisation; senior ministers still make clear in private that giving such rights to Turks may be impossible to sell to their voters.

The talks in Ankara between Turkish officials and Frans Timmermans, the commission’s vice-president, stretched into the early hours of Thursday. The draft deal was finally endorsed during a meeting with Mr Erdogan.