PREVIEW-Turkish PM to visit Iran amid foreign policy worries

* Visit to Iran comes as ties with Israel strained

* Some analysts concerned over foreign policy trends

By Ibon Villelabeitia

ANKARA, Oct 23 (Reuters) - Turkish Prime Minister Tayyip Erdogan's visit to Iran next week adds to concerns that Ankara may be slowly turning its back on its Western allies and seeking to regain its status as a regional power in the Middle East.

Following what Turks saw as Arab betrayal in World War One, Turkey made joining the elite club of Western powers its number one foreign policy objective, joining NATO in 1952 and first applying to join the European Economic Community in 1963.

Nearly 50 years on, Muslim Turkey is still kept at arms length by the European Union, but now having the world's 17th biggest economy, and half a million-strong army, it has the potential to become a powerhouse in its eastern backyard.

Erdogan has steadily expanded Turkey's influence in the Middle East since his Islamist-rooted AK Party took power in 2002. He travels to Iran at a time of worsening ties between Turkey and its regional ally Israel and as Ankara hails recent bilateral deals with Syria and Iraq as signalling a "new era".

But some analysts warn an erosion of Ankara's Western oriented foreign policy could have long-term consequences for NATO and for U.S. efforts from Afghanistan to Iraq.