Republican presidential candidate Donald Trump was met with an enthusiastic reception in the AIPAC conference in Washington on Monday, as he took a strong pro-Israel stance, blasting everyone from President Obama and the Palestinians to the UN and Iran.

"President Barack Obama is the worst thing to happen to Israel," the Republican frontrunner told the audience at the Verizon Center, castigating the U.S. president and his former Secretary of State Hillary Clinton for "pressuring our friends and rewarding our enemies."

In his speech, Trump softened two positions that have created unease among pro-Israel activists — his insistence on remaining “neutral” in brokering Israeli-Palestinian peace and his refusal to commit to recognizing Jerusalem as Israel’s capital.

On Jerusalem, Trump vowed to move the American embassy to the city, “the eternal capital of the Jewish people.” And he said the Palestinians must accept as a given the closeness of the U.S.-Israel relationship.

“The Palestinians must come to the table knowing that the bond between the United States and Israel is absolutely unbreakable,” Trump said. “They must come to the table willing to accept that Israel is a Jewish state and it will exist forever as a Jewish state.”

Trump placed the blame for the stalled peace talks on the Palestinians, saying that they have repeatedly refused Israeli and American overtures. Trump also accused the Palestinians of incitement to terrorism. "Children are being taught to hate the Jews, it has to stop," he said. "You cannot achieve peace if terrorists are treated as martyrs. That’ll end and it’ll end soon, believe me," he said to applause.

'United Nations is not a friend of democracy'

Trump also questioned the role of the United Nations in the peace process, saying any attempt by the international body to impose a Middle East agreement would be a disaster. The United Nations, saying it is "not a friend of democracy, not a friend to the U.S., and certainly not a friend to Israel," Trump said, promising that as president the U.S. would veto any UN Security Council resolution forcing a deal between Israel and the Palestinians.

"An agreement imposed by the UN would be a total and complete disaster. That's not how you make a deal," he said, warning that a UN resolution of this kind would only foster more Palestinian terrorism. Mentioning Taylor Force, the U.S. citizen killed in a terror attack in Jaffa earlier this month, Trump said that such behavior should not be rewarded. "You have to confront this kind of behavior," he said.

Trump delivered broadsides against his likely rival in the general election, Hillary Clinton, calling her a “total disaster” and blaming her for last year’s Iran nuclear deal. The line earned laughter and applause, although Clinton’s speech, earlier in the day, was well received.

Trump’s biggest applause line was when he began a sentence, “President Obama, in his final year – yay!”

AIPAC led opposition last year to the Iran nuclear deal and clashed repeatedly with the Obama administration in its unsuccessful bid to get Congress to nix the deal. Trump took aim at the deal with Iran and the removal of sanctions. "My number one priority is to dismantle the disastrous deal with Iran," he said to applause. Trump said the deal rewarded Iran with 150 billion dollars, while allowing it to "run out clock" and eventually acquire nuclear arms.

As president, Trump promised that he would stand up to Iran's push to destabilize the region, will work to dismantle its global terrorism network, and hold it "totally accountable" to the nuclear deal.

In a press conference ahead of his speech, Trump said that he would require Israel to pay back the United States for the foreign aid it received. Talking to reporters in Washington, Trump was asked about his previously stated stance that the U.S. should charge some of its allies for its assistance in their defense. "I want them to pay us some money," Trump said.