Donald Trump sought to win the support of the most powerful pro-Israel lobby group in the US on Monday.
The Republican frontrunner joined other presidential candidates in addressing the American Israel Public Affairs Committee (AIPAC) annual conference.
Although he has previously pledged to be "neutral" on the conflict, he told the 18,000 audience "there is no moral equivalency" between Israel and Palestine as he slammed the Palestinian Authority for fostering a society which glorified terrorists as "heroes" and "martyrs".
He told delegates that "the days of treating Israel like a second-class citizen will end on day one" of his presidency, after several had questioned his views on the Israel-Palestine conflict.
The build-up to the speech focused on pledges from some Jewish leaders to walk out in protest. However there did not seem to be any sign of protest as the New York billionaire spoke using auto-cues for the first time. He has previously ridiculed politicians for speaking for using prompts.
Trump spent much time criticising the Iranian nuclear deal as well the Palestinian government although he received his loudest cheers when he said Obama "may be the worst thing to happen to Israel" and called Hillary Clinton "a total disaster".
However Trump was heavily criticised by fellow Republican candidates Ted Cruz and John Kasich. Cruz attacked the frontrunner and said: "As president, I will not be neutral. America will stand unapologetically with the nation of Israel."
Cruz also picked up on Trump's referring to Palestine as a country. "Palestine has not existed since 1948" he said immediately after taking the stage.
Hillary Clinton, who leads the polls for the Democratic nomination, also laid into Trump for his wavering on Israel.
"We need steady hands, not a president who says he's neutral on Monday, pro-Israel on Tuesday and who knows on Wednesday," Clinton said to applause. "Israel's security is non-negotiable."
She continued, "We can't be neutral when rockets rain down on residential neighborhoods, when civilians are stabbed in the street, when suicide bombers target the innocent. Some things aren't negotiable, and anyone who doesn't understand that has no business being our president.
"Now, we've had dark chapters in our history before. We remember the nearly 1,000 Jews aboard the St Louis who were denied entry in 1939 and sent back to Europe. But America should be better than this. And I believe it's our responsibility as citizens to say so." Clinton said: "If you see bigotry, oppose it. If you see violence, condemn it. If you see a bully, stand up to him."