By Gulsen Solaker ANKARA (Reuters) - Turkish Prime Minister Tayyip Erdogan has ack**wledged his relations with U.S. President Barack Obama have soured, saying he had been disappointed among other things by a lack of U.S. action over the war in neighbouring Syria. Erdogan enjoys strong support in Turkey and is expected to become Turkey's first directly elected president in a vote on Aug. 10, but his leadership has left Turkey increasingly isolated on the global stage. Everything from his bombastic rhetoric on Israel to his *****down on anti-government protests last summer has raised concern among Western allies. Turkey has been an opponent of Syrian President Bashar al-Assad, backing rebels fighting to oust him and allowing the political opposition to organise on Turkish soil.