The European Union offered Turkey a possible $3.41 billion in aid and the prospect of easier travel visas and "re-energized" talks on joining the bloc in return for its help stemming the flow of migrants to Europe.
EU leaders at a summit in Brussels said they agreed on an "action plan" with Turkish President Tayyip Erdogan to cooperate on improving the lives of two million Syrian refugees in Turkey and encouraging them to stay put.
They also agreed to coordinate border controls to slow the influx of migrants crossing Turkey from Asia.
Though the plan put no figure on "substantial and concrete new funds" the EU would offer, German Chancellor Angela Merkel said the figure of 3 billion euros, which EU officials said Ankara had requested, had been discussed and seem reasonable.
"Our intensified meetings with Turkish leaders ... in the last couple of weeks were devoted to one goal: stemming the migratory flows that go via Turkey to the EU. The action plan is a major step in this direction," said summit chairman Donald Tusk, expressing "cautious optimism."
In formal conclusions agreed by the 28 national leaders at a meeting that ended after midnight, Turkey was offered an accelerated path to giving its citizens visa-free travel to the EU, provided it met previously agreed conditions.
Progress would also depend on Ankara showing real help in slowing migration and would be reviewed next spring.
Merkel, who will visit Istanbul for talks with Erdogan on Sunday in a political gesture two weeks before a Turkish general election, said it was clear that Europe's efforts to filter and process refugees would not work without Turkey's cooperation.
French President Francois Hollande stressed that Turks were not getting visas on easier terms. One condition is that Ankara must first stop granting such easy entry to Pakistanis, Afghans and others who end up heading to Europe.
It must also first sign and implement a previously agreed deal to take back from Europe migrantswho fail to win refugee status. "There must be no misunderstandings," Hollande said.
European governments are wary of granting full visa-free access to 78 million Turks. Any liberalization is likely to be limited at first to business travelers and students.
Leaders also agreed to "re-energize" moribund, decade-old negotiations on Turkey's application for membership of the European bloc, though they left open exactly how to do that.
"The accession process needs to be re-energized with a view to achieving progress in the negotiations in accordance with the negotiating framework and the relevant Council conclusions," they said, in language couched cautiously to reflect concerns in Cyprus and other states about easing off pressure on Ankara.
Earlier, at talks in Ankara with a delegation from the executive European Commission, Turkish ministers had asked the EU to start easing restrictions for some Turks traveling to the EU by the middle of next year, EU officials said.
EU sources said they sought $3.4 billion in new financial aid and the opening of six so-called chapters of the accession process, concerning harmonizing rules in energy, justice and economic and monetary affairs among others.
Turkey was also seeking more high-level political dialog with invitations for Erdogan to summits after an ice-breaking visit he made to Brussels earlier this month.