The US "desertion" of its long-time ally President Hosni Mubarak in the face of protests shaking the Egyptian regime has angered Israel, with analysts warning of consequences for the turbulent West Asia.

Until now, Israeli Prime Minister Benjamin Netanyahu's government has held back from any public criticism of the US position, to avoid a row with US President Barack Obama.

But Washington's change of heart towards the embattled Egyptian president has not passed unnoticed in Israel, where the dominant reaction has been one of criticism — in government circles, among analysts and in the press.

"One gets the impression that Washington was pretty anxious to throw Egyptian President Hosni Mubarak overboard" once he became a cumbersome ally, a senior Israeli official told AFP, on condition of anonymity.

"Even if the American position has become more nuanced in the last few days, it doesn't make it any less of a desertion. That's what is most worrying," he said.

"Loyalty is priceless, especially in the West Asia," he said, warning that Washington's sudden apparent ditching of the Egyptian leader could undermine the credibility of American foreign policy.

He also pointed to "confusion and incoherence of the American positions," referring to the declaration of support by an influential retired diplomat at the weekend, from which the Obama administration quickly distanced itself.

Dore Gold, a former ambassador to the United Nations who is close to Netanyahu, also highlighted such confusion.

He drew a comparison to the run-up to the 1979 Islamic revolution in Iran when the US administration of then president Jimmy Carter was faced with mass protests against the Western-backed Shah.

"Massive demonstrations were being held in the streets of Tehran, calling for the ouster of the shah, who had been America's key ally in the Persian Gulf.

"The White House did not know quite what to do: back the shah or seek his replacement," he wrote, warning the Obama administration not to "repeat the errors" it made by failing to back an ally facing protests, in the name of democracy.

Since the outbreak of the daily mass protests in Egypt on January 25, Israel has expressed fears that the rise of Islamist power in Cairo could threaten Egypt's 30-year-old peace deal with Israel and tip the regional balance of power.

"Everyone understands that Mubarak has to go, but we would expect the US administration to give him backing and not dissociate itself from him," the popular Yediot Aharonot daily said.

"For decades he was the mainstay of the West, the bulwark against Islamisation," it said.

"And when the US does this to the Egyptian President, what should any other ally of the US think?" the paper asked, warning about the "treacherousness" of the Western world and that it "could also happen to us."

For Eitan Gilboa, a professor of political science at Bar Ilan University, Washington "has stabbed its Egyptian ally in the back" when it could have criticised him in a more discrete fashion.

But Gilboa is not concerned that the Jewish state could one day face the same fate, given the huge support for Israel among the US public and the influential Jewish lobby.

In the short term, he believes Israel's position in the West could actually be strengthened by the move, especially if the Jewish state appears as "the only stable ally in the face of the Islamic threat."

For others, there is only one scenario to worry about.

"Israel has nothing to fear from the change in American policy, but much to fear from what is going on in Egypt," warned Shlomo Avineri, a political scientist from the Hebrew University of Jerusalem.

For him, the only fear is a rise to power by Egypt's Muslim Brotherhood, which opposes its 1979 peace treaty with Israel.