ATHENS (Reuters) -An Iranian-flagged tanker anchored off the Greek port of Piraeus is expected this week to retrieve part of its cargo of oil confiscated by the United States and sail back to Iran following a Greek court ruling, government sources said on Wednesday. The case has strained relations between Athens and Tehran amid growing tensions between Iran and the United States. The removal of oil from the Lana, formerly Pegas, prompted Iranian forces to seize two Greek tankers in the Middle East Gulf which have not yet been released. “The (Greek) Supreme Court’s ruling… is in Iran’s favour…