VIENNA (AFP) - UN chief Ban Ki-moon called Monday for renewed efforts to achieve a two-state solution in the Middle East following last week’s ceasefire between Israel and Hamas. “More than ever, we need a negotiated two-state solution ending the occupation and the conflict,” he said at the inauguration of a new centre for interreligious dialogue in Vienna. “I am determined to ensure that the ceasefire is sustainable. Both sides must adhere to the agreement,” Ban said of the truce achieved last Wednesday between Israel and Hamas after a week of deadly attacks on both sides.But this was not enough, he said. “The underlying issues must be addressed. This is critical to regional stability.