Philip Jacobson writes:
It is often said, only partly in jest, that Israelis examine every event of world significance through the prism of "will this be good or bad for us?" Well, they hardly need the doom-laden headlines in the Israeli press to tell them the continuing crisis on the streets of Cairo is as bad as it gets.
For the past three decades, the Jewish state's Middle East strategy has depended on the stable and, if not overly warm, effective working relationship with Egypt, the most important Arab nation of them all.
As a senior Israeli diplomat observes, ever since the signing of the historic peace treaty in 1979, "for the US, Egypt has been the keystone of its Middle East policy, [but] for us it's the whole arch." Reflecting the importance of this alliance, Israel's right-wing prime minister Benjamin Netanyahu has met with the Egyptian president Hosni Mubarak more often than any other foreign leader besides Barack Obama.
Apart from key economic factors - Israeli imports almost half of its natural gas from Egypt - this prolonged quiet on the Sinai front has profound military implications.
It is no secret that while the Israeli military periodically stages war games based on what might follow a collapse of the Mubarak regime, that threat has not featured high on the nation's strategic priorities agenda. Yet as documents recently made public by WikiLeaks have made clear, Egypt's sizeable military machine remains geared to an ultimate confrontation with the Israelis.
That helps to explain why Netanyahu, not known for his conciliatory views on Israel's Arab neighbours, now stresses the need to demonstrate "maximum responsibility, restraint and sagacity" in response to the crisis in Egypt.
As for the Obama administration, which inherited the Bush White House's strategy of holding its nose in the face of barbaric human rights abuses under Mubarak, the omens are foreboding.
The US has been pumping $1bn a year into Egypt to shore up the institutionally corrupt regime, yet the street uprising in Egypt's major cities has demonstrated that the most powerful and best organised political force on the scene today is the Muslim Brotherhood - implacably hostile to Israel and a covert supplier of weapons to Hamas fighters in Gaza.
Reports overnight that senior members of the Muslim Brotherhood and Hamas have escaped from jail in Egypt in recent days – with some members of the latter group finding their way back to Gaza through smuggling tunnels – will have caused huge concern for both Netanyahu and Obama.
And while the situation in Egypt remains "fluid" - diplomatic shorthand for no one having a clue what will happen next - no comfort will be taken in Jerusalem or Washington from the words of Eli Shaked, the wise and well-informed former Israeli ambassador to Cairo.
Writing in Israel's best-selling tabloid Yediot Aharonot the other day, he warned that if Mubarak is overthrown, a new militant Islamist regime will come to power, bringing with it a deep and abiding hostility to Israel and the West.
For good measure, he accused the US government, and by more direct implication Secretary of State Hilary Clinton whose vacillations have done nothing to defuse the crisis, of "taking the crucial developments in Egypt in a naïve fashion… expressing opinions that may be right for Western ears."
In short, when Clinton – joined by Obama and David Cameron - calls on Mubarak to allow an "orderly transition" to democracy, it only sets alarm bills ringing in Israel.