German Chancellor Angela Merkel (L), British Prime Minister David Cameron (C) and French President Francois Hollande (R) take part in a meeting at a European Union leaders summit in Brussels October 15, 2015. [Photo/Agencies]

BRUSSELS - The European Union offered Turkey a possible 3 billion euros ($3.4 billion) in aid and the prospect of easier travel visas and "re-energised" 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".