JERUSALEM — Israel’s conservative Likud Party initialed a coalition agreement with the center-left Labor Party early Tuesday, taking the prime minister-designate and Likud leader, Benjamin Netanyahu, a significant step closer to forming a broad government and avoiding leading a narrow right-wing coalition.

But the Labor leader, Ehud Barak, the current defense minister, is facing strong opposition within his party to the idea of sitting in a government led by Mr. Netanyahu. Some Labor opponents have warned of a split. The party’s central committee is expected to vote on whether to join the new government at a special convention later Tuesday.

Mr. Barak said last month that he would heed the will of the people and head into the opposition after his party’s dismal showing in the Feb. 10 elections. Interested in keeping his job as defense minister in the next government, he has since changed his mind.

Once dominant in Israeli politics, Labor won only 13 seats in the 120-seat Parliament.

Under the agreement reached between Likud and Labor negotiators after marathon talks over 24 hours, Mr. Barak will retain the defense portfolio. Shalom Simhon, the chief negotiator for Labor, told Israel Radio that the agreement states that the new government will work toward comprehensive peace in the Middle East. It does not contain any mention of the two-state solution as a goal for resolving the Israeli-Palestinian conflict, but Mr. Simhon noted, neither does the agreement explicitly rule that out.

The centrist Kadima Party, led by Tzipi Livni, the current foreign minister, has so far refused Mr. Netanyahu’s approaches to form a unity government. Kadima narrowly beat Likud in the election, but Likud was viewed as more likely to be able to form a coalition government.

Ms. Livni, who led the departing government’s negotiations with the Palestinians, made joining the new coalition conditional on Mr. Netanyahu’s acceptance of the two-state solution, and she also demanded full power-sharing, including a rotation of the prime ministership. Mr. Netanyahu does not advocate the idea of a sovereign Palestinian state, and says he wants to promote Palestinian economic development ahead of any political solution to the conflict.

Likud won 27 seats in the parliamentary elections and needs 61 to govern. Mr. Netanyahu has already reached coalition agreements with the nationalist party Yisrael Beitenu, led by Avigdor Lieberman, and with the ultra-Orthodox Shas. The addition of the smaller right-wing and religious parties would have brought the number to 65 seats.

But Mr. Netanyahu has made it clear he would prefer to lead a broad, less hawkish government. He contends that the formidable challenges facing Israel, like Iran’s nuclear program, require national unity. He would also like to avoid possible friction with the Obama administration.

Labor said it wanted a continuation of the peace process with the Palestinians, but did not insist on any declaration about the two-state solution in its talks with Likud. Instead, Labor focused on socioeconomic issues in the coalition talks, a priority for much of the party’s constituency. The Labor Party negotiators said they had made significant achievements on that front.

Mr. Barak has said he will be bound by the outcome of the party’s central committee vote. Mr. Netanyahu has until April 3 to finalize his coalition.

Also Tuesday, clashes broke out between police and demonstrators in the northern Arab Israeli town of Umm al Fahm after about 100 Israeli far-rightists marched on the outskirts of the town.

Police used tear gas and stun grenades to disperse local protesters who threw rocks and rioted against the right-wing march, which lasted half an hour, as planned. Sixteen police officers, including the deputy commissioner of the national force, were slightly injured by rocks, a police spokesman said.

The far-rightists had been planning to march in Umm al Fahm for months. They said they wanted to show that no part of Israel was off limits to them. The police banned a previous march, citing threats to public order and the rightists’ safety.

The police spokesman, Micky Rosenfeld, said that 2,500 police officers were stationed in and around Umm al Fahm on Tuesday morning to try to maintain order. Israeli and international organizations, meanwhile, continued to focus on allegations of Israeli Army misconduct during the recent military offensive in Gaza.

In a report presented to the Human Rights Council on Monday, the United Nations special rapporteur for the occupied territories, Richard Falk, concluded that Israel’s recourse to force in Gaza was not legally justified given the diplomatic alternatives available, and that it was “potentially a crime against peace.”

Israel said its campaign was primarily aimed at preventing rocket fire from Gaza into southern Israel.

Another report, presented to the council by a group of human rights advocates, listed more allegations of abuses. Radhika Coomaraswamy, the only member of the group allowed into Gaza after the war, accused Israeli soldiers of shooting Palestinian children, bulldozing a home with a woman and a child still inside and shelling a building they had ordered civilians into a day earlier.

Physicians for Human Rights-Israel published a report on Monday accusing the army of repeatedly violating its own ethics code, and possibly international law, by impeding the evacuation of the sick and wounded and by endangering medical teams operating in Gaza during the three-week war, which ended Jan 18.

In response, the Israeli military said its forces were “instructed to act with the utmost caution in order not to cause harm to medical vehicles and medical facilities.”

It added that efforts were complicated because Hamas, the Islamic group that controls Gaza, “methodically made use of medical vehicles, facilities and uniforms in order to conceal and camouflage terrorist activity, and in general used ambulances to carry terror activists and weapons.”

Just days ago the Israeli news media printed testimony by soldiers asserting loose rules of engagement in the war in Gaza, which they said led to civilian deaths and wanton property destruction.

In a speech to army recruits on Monday, the chief of staff, Lt. Gen. Gabi Ashkenazi, said he did not believe that Israeli soldiers had hurt civilians “in cold blood,” and he called the Israeli Army the “most humane army in the world.” He added that “isolated cases, if found to have taken place, will be dealt with individually.”

The Israeli military police have opened an investigation.