The Blue and White party leader Benny Gantz said on Saturday he had accepted an invitation to meet U.S. President Donald Trump in Washington on Monday to discuss a peace plan for the Middle East.
Gantz is said to meet the American president separately from his main domestic political rival of Prime Minister Benjamin Netanyahu, who is also travelling to Washington to meet Trump.
But Palestinian leaders have warned that no deal can work without them on board.
Trump invited both Israeli leaders to hear details of the White House's long-delayed peace plan ahead of ans Israeli election in March, the third in less than a year.
Israeli political analysts had viewed the U.S. invitation as a pre-election boost to Netanyahu, who heads the right-wing Likud Party and is Israel's longest-serving prime minister.
Gantz, a former general, heads the centrist Blue and White Party. His attendance in Washington had been in doubt, but on Saturday night he said that he had been in contact with senior White House officials for months and that he had decided to go.
"These are fateful times both for Israel's borders and character, as well as its democratic fabric," Gantz said in broadcast remarks.
"The peace plan devised by President Trump will go down in history as a meaningful landmark mapping the way for the different players in the Middle East to finally move forward towards an historical and regional agreement," Gantz added.
Netanyahu also issued a statement on Saturday calling the Trump initiative a "once in history" opportunity.
POLITICAL ASPECTS
The launch of Trump's plan to end the decades-long conflict between Israel and the Palestinians has been delayed numerous times over the past two years.
The political aspects of the peace initiative have been closely guarded. Only the economic proposals, including a $50 billion investment plan put forward by Trump advisor Jared Kushner, have been announced.
A source familiar with the peace team's thinking said bringing both Netanyahu and Gantz in on the details is aimed at defusing any suggestion that Trump might be favouring one Israeli candidate over another.
Israeli-Palestinian peace talks collapsed in 2014 and Palestinians have called Trump's proposal dead in the water even before its publication.
The Palestinian leadership said that there had been no communication with the Trump administration.
Following Gantz's announcement that he would go to Washington, Palestine Liberation Organisation executive committee member Wassel Abu Youssef told Reuters:
"Blue and White and Likud are two faces of the same coin. There is an alliance between the U.S. administration and the Israeli parties running into the election."
Speaking in the West Bank city of Ramallah, he added: "We will not accept the 'Deal of the Century' and there is no power on earth that can force the Palestinian people to concede their rights, represented in establishing their independent state, with Jerusalem as its capital."
Palestinian President Mahmoud Abbas has said Washington can no longer be regarded as an honest mediator, accusing it of pro-Israel bias. This followed a series of Trump decisions that delighted Israel but dismayed and infuriated Palestinians.
These included recognising Jerusalem as the capital of Israel, moving the U.S. Embassy from Tel Aviv to Jerusalem and slashing hundreds of millions of dollars in humanitarian aid to the Palestinians.