Sharon says "this stage" of Israeli offensive over JERUSALEM, April 21 (Reuters) - Prime Minister Ariel Sharon declared an end to "this stage" of Israel's West Bank offensive on Sunday after tanks rumbled out of two more Palestinian cities. The army said it had left Ramallah, apart from Palestinian President Yasser Arafat's compound, and pulled out of Nablus. But it kept up a siege of a Bethlehem church where gunmen are holed up. "We have finished this stage of the operation called Defensive Shield," Sharon told reporters. "We have achieved very profound results but the struggle against terrorism continues. However this time, it will work...