By Adrian Croft
BRUSSELS (Reuters) - The European Union will press Turkey to cooperate more closely in the fight against Islamic State and urge it not to undermine EU sanctions on Russia on a visit this week intended to give new impetus to often fraught EU-Turkish relations.
EU foreign policy chief Federica Mogherini, Enlargement Commissioner Johannes Hahn and Humanitarian Aid Commissioner Christos Stylianides will travel to Turkey on Monday and Tuesday in one of the highest-profile EU visits in years.
"The visit ... is a strong indication of the strategic importance of the EU-Turkey relationship and our desire to step up engagement," Mogherini said in a statement.
Turkey has been negotiating to join the EU since 2005, but political obstacles, notably over the divided island of Cyprus, and resistance to Turkish membership from some EU countries, have slowed progress and relations have often been difficult.
But now top EU officials hope a new president and prime minister in Turkey and a new European Commission in Brussels mark a fresh start that will pave the way for regular high-level talks to discuss common strategic interests.
The visit comes a week after Russian President Vladimir Putin's trip to Turkey, during which Moscow announced it was scrapping the South Stream gas pipeline project and named Turkey as its preferred partner for an alternative pipeline.
EU officials want to talk about the need for closer cooperation in the fight against Islamic State militants and other militant groups and efforts to cut off their funding and halt the flow of foreign fighters.
Thousands of Europeans have gone to fight in Syria, with Islamic State or other groups, and Turkey is a key transit point. Turkey says EU governments should be doing more to stop would-be fighters traveling to the region.
The EU wants Turkey's help in identifying foreign fighters and in warning of any risks to aviation security, one EU official said on condition of anonymity.
Turkey has not joined Western sanctions on Russia over Ukraine. EU officials will continue to press Turkey to join in sanctions or at least not to take advantage of the situation by exporting affected products to Russia, the official said.
The EU officials will meet Turkish President Tayyip Erdogan and Prime Minister Ahmet Davutoglu and visit a refugee camp. They will announce an increase in EU aid to help Turkey cope with an influx of refugees from Syria and Iraq.
(Editing by Andrew Heavens)