An essay by American journalist Peter Beinart in the New York Review of Books, claiming that "Morally, American Zionism is in a downward spiral", has provoked a storm among supporters of Israel in the US.

Mr Beinart, a former editor of the pro-Israel New Republic and a one-time supporter of the Iraq War - in other words, no bleeding-heart liberal - said he fears that Zionism will soon have little to offer liberal Americans. He lays the blame squarely at the door of "the Jewish establishment".

With their uncritical support of Israel and knee-jerk attacks on dissent, AIPAC, the Conference of Presidents of Major American Jewish Organisations and the Anti-Defamation League have pushed Zionism too far to the right, he said.

"Particularly in the younger generations, fewer and fewer American Jewish liberals are Zionists; fewer and fewer American Jewish Zionists are liberal," he wrote in the Review's June issue.

"One reason is that the leading institutions of American Jewry have refused to foster - indeed, have actively opposed - a Zionism that challenges Israel's behavior in the West Bank and Gaza Strip and toward its own Arab citizens. For several decades, the Jewish establishment has asked American Jews to check their liberalism at Zionism's door, and now, to their horror, they are finding that many young Jews have checked their Zionism instead."

The result, said Mr Beinart, is that Zionism is increasingly only attractive to socially conservative, Orthodox Jews. Meanwhile, the American Zionist movement is becoming ever more willing to turn a blind eye to more extreme views in Israel. If the trend continues, Mr Beinart fears that American liberals will lose all interest in Israel and American Zionists will lose all interest in human rights.

ADL national director Abraham Foxman called Mr Beinart's essay "an over-exaggeration".

"I don't think liberal Zionism is any greater or lesser today," Mr Foxman said. "But the peace process is at a stalemate, so there is a lot of frustration."

According to Mr Foxman, right-wing Zionism, which has grown considerably over the past 30 years, is still dwarfed by the left wing, which he maintains has always dominated.

Besides, Mr Foxman says the left-versus-right argument is a distraction from a larger problem - that generations of American Jews have been raised with little, if any, consciousness of Israel or of Zionism altogether.

"Most don't even know what the word Zionism is," said Mr Foxman.

Nevertheless, he sees a vibrant debate between the left and right about how Israel can progress.

"What's really brought it to life is the election of a liberal Democrat President," said Mr Foxman. "It's given more life and vitality to the liberal movement In the US."

About three-quarters of American Jews voted for Barack Obama. And the emergence of dovish Israel lobby J Street, in America, and J Call, in Europe, do point to a renewed vigour among the pro-Israel, pro-peace, left.

But historian Tony Judt, who sparked controversy in 2003 with an essay arguing in favour of a binational state of Jews and Arabs in Israel, concurred with Mr Beinart's view.

"It's my guess that within a decade, Zionism will be almost exclusively associated with extreme conservatism in politics and orthodoxy in religion - the very reverse of its traditional constituency."