New York (AFP) - When Bernie Sanders called Israel's response in the 2014 Gaza war disproportionate and urged America to be more balanced on the Israeli-Palestinian conflict, he smashed a presidential campaign taboo.

His remarks at the April 14 Democratic debate ahead of New York's decisive primary on Tuesday amounted to unprecedented criticism of Israel and promotion of Palestinian rights from a canvassing US presidential candidate.

Israeli Prime Minister Benjamin Netanyahu "is not right all of the time," said the Vermont senator. "We cannot continue to be one-sided."

He criticized Democratic frontrunner Hillary Clinton for not saying that she would do more to promote Palestinian rights when she addressed the powerful right-wing American Israel Public Affairs Committee (AIPAC) lobby in Washington in March.

"If we are ever going to bring peace to that region, which has seen so much hatred and so much war, we are going to have to treat the Palestinian people with respect and dignity," Sanders said.

But Sanders' words reflect changing attitudes among Jewish voters, particularly Millennials who grew up seeing Israel as a strong state and for whom the horrors of the Holocaust are more removed.