Republican presidential front-runner Donald Trump on Monday vowed an unbreakable U.S. alliance with Israel if he is elected president in November, seeking to clear up confusion — and criticism from his rivals — over his repeated pledges to remain neutral in any peace negotiations between Israelis and Palestinians.

Trump's speech to the American Israel Public Affairs Committee, a powerful pro-Israel lobbying group, was part of a daylong effort by the anti-Washington candidate to persuade establishment Republicans to get behind his insurgent candidacy and give up on an effort to deny him the party's presidential nomination.

Trump told the crowd at AIPAC he supported moving the U.S. embassy in Israel to contested Jerusalem; promised to meet immediately with Benjamin Netanyahu, Israel's prime minister and occasional rival of President Barack Obama; vowed to dismantle the Iran nuclear deal; denounced Palestinian terrorism; and said he'd protect Israel from hostile resolutions at the United Nations.

"We will move the American embassy to the eternal capital of the Jewish people, Jerusalem," said Trump. "We will send a clear signal that there is no daylight between America and our most reliable ally, the state of Israel."

The speech got a relatively warm response, amid some grumbles from the crowd.

He has described himself as extremely pro-Israel, but has said he would take a "neutral" stance in trying to negotiate an elusive peace settlement between Israel and the Palestinians.

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Ted Cruz says that as president he would 'stand unapologetically with the nation of Israel.' (Brendan Smialowski/AFP/Getty Images)

Rivals question Trump's stance on Israel

Trump's critics have said he could harm long-standing U.S. support for Israel. Trump's leading Republican rival, U.S. Senator Ted Cruz, reminded the AIPAC gathering of Trump's position.

"Let me be very, very clear," Cruz said. "As president I will not be neutral. America will stand unapologetically with the nation of Israel."

Additionally, Cruz agreed with Trump on the issue of moving the U.S. embassy to Jerusalem.

Democratic presidential front-runner Hillary Clinton, a former secretary of state, used her AIPAC appearance to attack Trump.

"We need steady hands, not a president who says he's neutral on Monday, pro-Israel on Tuesday and who-knows-what on Wednesday because everything's negotiable," she said.

Clinton also took aim at Trump's vow that, if elected, he would deport illegal immigrants and bar Muslims temporarily from entering the U.S.

"If you see bigotry, oppose it, if you see violence, condemn it, if you see a bully, stand up to him," she said.

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Hillary Clinton criticized Trump at the AIPAC gathering for being 'neutral on Monday, pro-Israel on Tuesday.' (Saul Loeb/AFP/Getty Images)

Ohio Gov. John Kasich touted his experience at AIPAC and took subtle shots at Trump.

"I don't need on the job training," he said, adding he already knows about the dangers facing the U.S. and its allies.

The Ohio governor also stressed his "firm and unwavering" support for the Jewish state and vowed to work to stamp out intolerance, racism and anti-Semitism.

But some of his loudest applause came as he appeared to take on Trump.

"We are Americans before we are Republicans and Democrats," he said, adding: "I will not take the low road to the highest office in the land."

Unlike some of his Republican rivals, Kasich for months did not pledge to "rip up" the multi-nation Iran nuclear deal on his first day in office. But he is now calling for a suspension in the U.S. involvement in the deal in response to recent ballistic missile tests, which he says are a violation.

Sanders criticizes Netanyahu, Hamas

Democrat Bernie Sanders says the United States should have unwavering support for Israel, but any Middle East peace solution must recognize civil rights of the Palestinian people.

The Vermont senator criticized Netanyahu's administration for the construction of Jewish settlements in the West Bank and withholding tax revenues from the Palestinians. But he criticized leaders of Hamas and the organization's attacks on Israel.

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Bernie Sanders, who did not attend the AIPAC event, said in a speech in Utah he's the only presidential candidate with personal ties to Israel. (George Frey/Getty Images)

Sanders delivered a foreign policy address in Salt Lake City during a western campaign trip that prevented him from speaking at the AIPAC conference in Washington.

Sanders said the speech is one he would have given before the pro-Israel lobbying group, where Democratic rival Hillary Clinton and the three Republican candidates were speaking Monday.

Sanders, who is Jewish, said he's the only presidential candidate with personal ties to Israel and that he served on a kibbutz as a young man.

With files from The Associated Press