A woman was killed and 40 others wounded when a suicide bomber detonated himself yesterday in Dimona. A second suicide bomber, stunned by the first blast, was killed by an alert police officer before he could explode himself, saving many lives. At this writing, it is not clear whether the terrorists came from Gaza via Sinai and crossed into Israel, or whether they came from the West Bank. There is no serious barrier to either access route, because the southern portion of the security fence in Judea and Samaria has not been completed, and Israel's border with Egypt also has not been secured with a proper fence. That terrorists have moved from Gaza into Egypt is clear enough. On Saturday, two brothers from Gaza wearing explosive belts were caught in the Sinai by Egyptian security forces. A day earlier, Egypt arrested 15 Palestinian terrorists, 12 of whom were members of Hamas. Last week, Egypt arrested another five Palestinians carrying explosive belts. These arrests, however welcome and necessary, are not near enough. Whichever route yesterday's bombers took, the wide-open border between Israel and Egypt is "a disaster waiting to happen," as this newspaper editorialized just one week ago. To their credit, at Sunday's cabinet meeting, before yesterday's attack, ministers Ehud Barak, Haim Ramon, and Binyamin Ben-Eliezer all called to build a new security fence along the border with Egypt. As we have pointed out previously, however, this is nothing new. An IDF plan to build such a barrier, called Hourglass, was put forward in early 2005 and endorsed by Ariel Sharon, but only NIS 100 million - out of an estimated cost of NIS 1.5 billion - was actually found to pay for it. Promises are cheap and have been repeatedly broken. A plan and the rhetorical support of ministers are worth nothing without a commitment to find the budget to fund this project. If Barak and Prime Minister Ehud Olmert truly support Hourglass, they need to find the money to fund it now, before the current promises disperse with the wind like all the others. But that is not all. Shin Bet (Israel Security Service) head Yuval Diskin told the same cabinet meeting that during the 12 days that Gaza-Egypt border was wide open, Hamas brought in significant numbers of long-range rockets and anti-tank and anti-aircraft missiles. This flow of weaponry into Gaza was already constant, through smuggling tunnels and other means. The destroyed border only added to the seriousness of the problem. Accordingly, the urgent task is both for Israel to complete the missing sections of the West Bank security fence and seal its border with Egypt and, critically too, for Egypt to seal its border with Gaza. We cannot go back to the status quo ante, where weapons and money flowed into and terrorists flowed into and out of Gaza courtesy of Egypt's blind eye. It is completely irresponsible for Egypt to allow Hamas to strengthen itself in Gaza, even aside from Israel's interests and Egypt's responsibilities toward the peace process that the US has been trying to launch. Hamas, after all, is allied to the Muslim Brotherhood, which Egypt has ruthlessly suppressed for years. Evidently, the Egyptian government feels little external or internal pressure to take serious steps to cut off Hamas's weapons lifeline. The fault for this lack of pressure lies with the US, but first and foremost, with Israel. The US has quietly and ineffectively raised the issue with Egypt for years. But it is understandable that the US government cannot get itself more exercised about the problem than Israel is. And it is seems that Olmert places his relationship with President Hosni Mubarak above the emphatic, insistent pursuit of the demand that Egypt shut down the weapons flow to Gaza. This must change. Initially, it may have been legitimate to try soft-pedaling with Mubarak, but that approach has failed. Israel must make clear that what passes for normal relations, including the pilgrimages to Sharm e-Sheikh and praise for Mubarak, are over so long as Egypt paves the road toward the next Israeli-Palestinian war. Further, Israel should actually do what Egypt anyway accuses Israel of doing: press the US to treat Egypt like Syria so long as Cairo acts like Damascus. True, Damascus would openly arm Hizbullah, while Cairo is more passively arming Hamas, but the result is the same. Just as allowing Hizbullah to build up for six years led to war in the North, what Egypt is failing to do now will lead to war in the South. Rather than wait for this war, and for the Winograd-style committee that will follow it, the time to cut Hamas's weapons lifeline is now.