BEIT LAHIYA, Gaza Strip — Mideast envoy Tony Blair on Tuesday called off what would have been the first visit of a top Western diplomat to Hamas-ruled Gaza, after Israel's Shin Bet security service said he might come under attack there. The Shin Bet security service said it had received "pinpoint information that Palestinians were planning to attack Blair in Gaza, so the relevant services alerted him to the fact." Blair told The Associated Press that the threat was "specific" and "credible," forcing him to call off the trip but he said it was a postponement, not a cancellation. "I intend to go to Gaza as soon as I can, and I will continue to press for help for the people there," he said. Blair's visit Tuesday was to have included a tour of a Gaza waste water project and meetings with traders and U.N. officials, but not with leaders of Hamas, the Islamic militant group that seized Gaza by force more than a year ago. Hamas made security arrangements for Blair, setting up checkpoints in areas he was expected to tour, banning cars from using roads and lining streets with black-clad policemen carrying AK-47s. Since the Hamas takeover, Gaza has been virtually sealed off from the world by Israel and Egypt, a policy that has received tacit international backing. Blair has said in recent weeks that a new policy toward Gaza needs to be developed, pointing to the growing suffering of Gaza's people, but has not offered a plan. The options ar ...