Palestinians cannot fulfill their national aspirations through a unilateral appeal to join international institutions, the head of Israel’s opposition said on Tuesday.

Speaking at a conference in Jerusalem titled “Israel, US and the Middle East: New Visions,” organized by Israeli left-wing research center Molad and the Center for American Progress, a Washington-based progressive think tank, Labor Party chairman Isaac Herzog addressed the possibility of Palestinian unilateral action if Israel fails to accept Palestinian preconditions for extending talks beyond April.

“[PA leader Mahmoud] Abbas should understand that there’s no unilateral avenue,” Herzog told the audience. “He has no alternative in any UN forum. It will bring no solace to his people.”

Herzog added that the only viable option at the moment is “pressing both sides to negotiate.”

The Israeli opposition leader was speaking as Palestinian leaders were preparing to discuss an American offer for extending negotiations, presented by Secretary of State John Kerry to chief Palestinian negotiator Saeb Erekat on Monday evening, and reported to include the release of American-Israeli spy Jonathan Pollard.

Herzog reiterated his commitment to support Prime Minister Benjamin Netanyahu in any bid to bolster peace talks with the Palestinians, noting that he heads a Knesset “peace bloc” encompassing 59 members of Knesset outside the governing Likud party willing to endorse continued negotiations.

“There is a clear, unequivocal majority [in the Knesset] for peace,” he said.

Bahraini Crown Prince Salman bin Hamad Al Khalifa, second right, attends the opening session of the Arab League Summit in Bayan Palace, Kuwait City, Tuesday, March 25, 2014 (photo credit: AP/Nasser Waggi)

Bahraini Crown Prince Salman bin Hamad Al Khalifa, second right, attends the opening session of the Arab League Summit in Bayan Palace, Kuwait City, Tuesday, March 25, 2014 (photo credit: AP/Nasser Waggi)

The Arab Peace Initiative, first presented by Saudi Arabia in 2002 and endorsed by the Arab League in 2007, should be the basis for future talks, Herzog argued.

“We need the Arab League as a partner for future progress,” he said, calling for a “full fledged” implementation of the plan.

Referring to the security issue following a visit earlier today to the Israeli border with Syria on the Golan Heights, Herzog said that security should not be considered a subject associated exclusively with the Israeli right.

He mentioned historic Israeli shortcomings in ensuring proper security arrangements in two cases: the IDF withdrawal from the Philadelphi Route on the border between the Gaza Strip and Sinai (which Israel withdrew from in September 2005, leaving the area under the control of the Egyptian army); and the security provisions in the Sinai Peninsula under the Camp David Peace Accords, which Israel signed with Egypt in March 1979.

Briefly addressing the situation in Syria, Herzog said the country now faces a choice between “bad and worse” Islamists. He said that Syrian opposition leaders with whom he has been in touch over the past few years have voiced grave concern over the country’s future.