By Alastair Macdonald AMSTERDAM (Reuters) - The European Union is far from satisfied yet with the results of Turkish efforts to hold back migrants sailing to Greek islands and will discuss the problem in Ankara on Monday, a senior EU official said. Frans Timmermans, the deputy head of the executive European Commission, told a news conference on Thursday that data showed arrivals in Greece in recent weeks had shown little change since the EU pledged cash and other concessions to Turkey on Nov. 29 in return for Turkish help in curbing irregular immigration. "Over the last couple of weeks, the figures have remained relatively high, so there is still a lot of work to do there," Timmermans said in Amsterdam, noting that he would travel to Turkey for talks on Monday to address a crisis that has divided EU governments and bolstered anti-EU nationalists.