A Palestinian woman with explosives strapped to her body blew herself up in a suicide attack at a West Bank checkpoint, wounding at least two Israeli police officers and killing two other Palestinians in her car, Israeli military sources said. The attack is the latest incident of violence at Israeli checkpoints, where Palestinian militants have used ambush tactics to kill Israeli soldiers. And it comes at a delicate time, with Saudi Arabia pushing a plan that would provide for the Arab world normalizing relations with Israel, in return for an Israeli withdrawal to its borders before the 1967 Six Day War.