Washington (CNN) President Donald Trump's nominee to be the next US ambassador to Israel faced a grilling from senators a day after Trump backed off the long-held US and international position that the key to Middle East peace lies in a two-state solution.

That shift, which Trump revealed Wednesday at a White House news conference alongside Israeli Prime Minister Benjamin Netanayahu, is just one reason the confirmation hearing for David Friedman, a New York bankruptcy lawyer, immediately veered into contentious territory. Protestors repeatedly interrupted the proceedings in the Senate Foreign Relations Committee and lawmakers assailed Friedman for previous comments they deemed insulting.

Friedman has backed Israeli settlements, which are seen as illegal under international law and as an impediment to a peace deal by Palestinians. He has called Palestinian statehood an "illusion," raised millions of dollars for a settlement near the Palestinian city of Ramallah in the West Bank and he has excoriated critics in print, referring to a liberal Jewish group as "kapos," the word for Jews who cooperated with Nazis during the Holocaust.

Lawmakers quizzed the ambassador-designate on his position on statehood in the wake of Trump's remarks. In answer to a question Wednesday, Trump said that he was "looking at two-state and one-state and I like the one that both parties like."

He added that, "I can live with either one. I thought for a while that two-state looked like it might be the easier of the two, but ... if Israel and the Palestinians are happy, I'm happy with the one they like the best."

On Thursday, Trump's ambassador to the UN, Nikki Haley, said of the administration that "we absolutely support a two-state solution, but we are thinking out of the box as well, which is: What does it take to bring these two sides to the table?"

Over the course of Thursday's confirmation hearing, Friedman walked back many of his previous public statements, saying that the two-state solution "remains I believe the best possibility for peace in the region" and that settlements "may not be helpful." Any future Palestinian state would ideally be "demilitarized," he said, Israel retaining control over the western border with Jordan.

And he pushed for a focus on Palestinian economic development instead, which many Palestinians see as a delaying tactic for coming to a peace deal.

Sen. Benjamin Cardin of Maryland, the ranking Democrat on the Senate Foreign Relations Committee, questioned Friedman's dismissal of the two-state solution as a "damaging anachronism" and told him his views "constitute an unprecedented break" from US policy.

Friedman answered that if the Israelis and Palestinians were able to reach an agreement "through direct negotiations along parameters agreeable to them ... I would be delighted to see peace come to this region where people have suffered on both sides for so long."

He continued, "I have expressed my skepticism solely on the basis of my perception of the Palestinians' failure to renounce terror and accept Israel as a Jewish state."

In a February 2016 article in an Israeli newspaper, Friedman described the idea of a two-state solution as a "scam."

Friedman went on to mentioned the 1993 Oslo Accords' requirement that Palestinian leaders end incitement against Israel: "We haven't made progress since then. In the aftermath of Oslo, terrorism has increased four-fold."

He made no mention of Israeli actions such as settlement construction, the destruction of Palestinian homes and seizure of Palestinian land in the West Bank as possible obstructions to a peace agreement or drivers of violence.

And he said that if there are attempts to move forward on Israeli-Palestinian diplomacy, it should happen behind closed doors.

"I happen to believe that with respect to the state of Israel, discretion is incredibly important and public comments can be defeating," Friedman said. "If there's progress to be made in the Middle East and the peace process, it's through private diplomacy ... behind the scenes."

At one point, Republican Sen. Marco Rubio of Florida asked whether Friedman thought Palestinians were the major obstacle to peace; whether he disagreed with the "orthodoxy" that the US needs to be an honest broker between Israel and the Palestinians; and whether he felt "professionals in the State Department and the foreign policy elite" unfairly maligned Israel.

"Yes," Friedman replied.

New Jersey Sen. Robert Menendez, a Democrat, noted that Friedman is "very passionate about Israel," and then asked Friedman to assure the committee that his loyalty and commitment lay with the US. Friedman agreed that it does.

But much of the hearing was taken up with rhetoric rather than policy.

As Friedman began his opening remarks, a series of protesters stood to denounce him, interrupting him at regular intervals.

"We will not be silent, you do not represent us and you will never represent us," shouted one young man wearing a kippah, the Jewish head covering.

A young man waving a Palestinian flag shouted that in the West Bank, "Palestinians are there and will always be there."

Even before Friedman began speaking, his representatives tried to defuse anger about some of the insults he has previously leveled at President Barack Obama and members of Congress.

Sen. Lindsey Graham, a South Carolina Republican, introduced Friedman to the panel, saying the "deal-making bankruptcy lawyer" is "very passionate, he has said some things I don't agree with, but ... what's encouraging to me is he's said, 'Maybe I should watch my rhetoric.' "

New Mexico Sen. Tom Udall detailed many of the insults Friedman had hurled in print before being selected for the ambassadorial role.

"He has insulted and denigrated members of the Senate," Udall said. He quoted Friedman's comment about senior Democratic New York Sen. Charles Schumer, after Democratic colleagues voted to approve the Iran nuclear deal, that "Schumer is validating the worst appeasement of terrorism since Munich," where Palestinian terrorists killed Israeli athletes at the Olympic Games.

Udall also said that Friedman had "slandered" President Barack Obama when he described "the blatant anti-Semitism emanating from our president and his sycophantic minions."

And he pointed out that Friedman once said of the Anti-Defamation League that "frankly, they sound like morons."

The ADL released a statement Thursday saying that Friedman had expressed regret for his words. "We accept his apology and appreciate his outreach," the ADL said. Friedman will "represent all segments of the Jewish community and the broader country."

Democratic senators, however, told Friedman that his use of rhetoric raised questions about whether he was suited for the job and whether he would represent all Americans.

"The language you have regularly used against those who disagree with your views has me concerned about your preparedness to enter the world of diplomacy," Cardin said.

Sen. Christopher Coons, a Delaware Democrat, put it unusually bluntly: "Your comments have been "intemperate inappropriate and insulting."

Friedman didn't try to defend himself, telling Cardin at one point that "there is no excuse. If you want me to rationalize or justify it, I can not. I regret" using those words.

But he also made clear he was apologizing only for his word choices, not for his positions. "I have profound differences of opinion with the J Street Organization," the group he compared to Nazi collaborators. "My regrets are as to the language and the rhetoric," he said. "I'm not withdrawing my personal views as to the organization."

Sen. Rand Paul, a Kentucky Republican, pressed Friedman about Trump's announcement that he would move the US Embassy from Tel Aviv to Jerusalem, a highly sensitive issue traditionally left for final status negotiations as both Israelis and Palestinians claim the city as their capital.

That announcement was originally folded into Trump's statement that the New York lawyer was his pick for ambassador to Israel. The President has since walked it back, saying Wednesday that, "I'd love to see that happen. We're looking at it very, very strongly. We're looking at it with great care, great care, believe me, and we'll see what happens."

"There will be ramifications if we move" the embassy, Paul told Friedman, and went on to ask if he was "a thoughtful individual" who would think through the implications of a move with the President. "Will it be worth our while," he said.

"The decision obviously will be made by the President and I will support him considering the political, security and other ramifications of it," Friedman said.