Berlin and Ankara are at loggerheads over Europe’s refugee crisis, with Germany refusing to take in refugees directly from Turkey unless it does more to curb the number of migrants arriving in Greece.

Angela Merkel, German chancellor, told the Bundestag on Wednesday it was “ridiculous” to resettle registered refugees from Turkey while up to 2,000 people a day were still crossing the Aegean Sea to enter EU territory.

Turkish officials have been insisting a resettlement scheme — whereby some of the 2m Syrian refugees in Turkey would be transferred to countries across the EU — should not be directly linked to a reduction in irregular migrant flows, insisting they have already done enough to warrant EU assistance.

The mounting tensions came ahead of a meeting in Brussels on Thursday that had been scheduled between Ms Merkel and Ahmet Davutoglu, her Turkish counterpart, on the sidelines of a two-day summit. However, the meeting was cancelled after a bomb exploded in Ankara on Wednesday, killing at least 28 people. Mr Davutoglu cancelled his trip to Brussels.

The Turkish and German leaders were due to discuss the resettlement scheme in a meeting with Alexis Tsipras, the Greek prime minister, before a “mini-summit” with eight other leaders.

The Berlin-backed resettlement scheme would see up to 250,000 people a year moved from Turkey to willing EU member states.

Turkish officials said they remained hopeful of an agreement that would commit both sides to reducing the flow and to implementing the resettlement scheme — but without making one conditional on the other.

Ms Merkel appeared to dash those hopes in her Bundestag remarks, which amounted to a significant hardening of Berlin’s stance towards Turkey together with an attempt at easing tensions within the EU over migrant flows. German officials said winning back control of Europe’s external borders was “the central political element” they had to deal with before they could consider other issues.

“At this [summit], it’s not a matter of agreeing quotas,” Ms Merkel said. “We make ourselves in Europe look ridiculous . . . would be taking the second step before the first.”

Although 11 EU member states have agreed in principle to the scheme, member states are divided over how it will work, with some calling for an outright halt in people crossing the Aegean before resettlement can begin while others call for leniency, according to diplomats.

Among the options being floated is a plan to merge the EU’s relocation scheme — which is supposed to move 160,000 refugees who have already arrived in Greece and Italy to other member states on a quota basis — with the separate scheme of taking in refugees directly from Turkey.

Under the merger proposal, member states would be able to count any refugees accepted from Turkey as part of their “relocation” quota. While member states in, for instance, central Europe are vociferously opposed to taking in refugees who have already arrived in the EU, they are more open to taking them in directly from Turkey, according to diplomats from the region.

EU leaders are rushing to complete a deal with Turkey before an expected jump in the number of people making the trip when the weather improves in the spring. Diplomats fear a sharp increase in numbers will weaken the EU’s position in negotiations, and some have warned Ankara their window for striking a deal is rapidly closing.

Until now, Ms Merkel had been accused in some EU capitals of kowtowing to Turkish President Recep Tayyip Erdogan, including with a high-profile pre-election visit to Istanbul in November. Her tougher stance appears intended to show an increasingly sceptical German public she can act firmly in advance of next month’s elections in three regions.

Ms Merkel is also trying to close growing divisions in the EU between Germany and its critics and head off a push by the central European states led by Poland to help close the Macedonian-Greek border.

Austria announced on Wednesday it would cap the number of migrants it would allow to cross into the country at 3,200 daily and would accept only 80 applications for asylum a day.

Werner Faymann, the Austrian chancellor, told local press that he believed Ms Merkel would soon have to follow a similar route, but in the Bundestag she said she remained committed to the current course and did not support efforts — backed by central and eastern Europe — to seal Greece’s border to prevent migrants from transiting north.