Details of the latest Middle East peace plan began to emerge today, hours after John Kerry announced that he had brokered an agreement that is likely to lead to fresh talks between the Israelis and Palestinians.

The most significant concession appears to be a promise by Israel to release a number of high-ranking Palestinian prisoners, many of whom have been behind bars for decades. Jail releases have been a long-standing demand of the Palestinian leadership, which regards the individuals as ‘political prisoners’. The Israeli government disputes that view.

“There will be some release of prisoners,” Yuval Steinitz, Israel’s hawkish strategic affairs minister, told Israel Radio. “I don’t want to give numbers but there will be heavyweight prisoners who have been in jail for tens of years.” It is understood that the prisoners will be released in stages.

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Mr Steinitz’s comments came less than 24 hours after Mr Kerry said that the two sides had agreed to restart negotiations for the first time since 2010. While the deal was hailed in some quarters as a resumption of direct talks, it appears to fall some way short of that.

Speaking in the Jordanian capital, Amman, on Friday evening, Mr Kerry said that the two sides had “reached an agreement that establishes a basis for direct final-status negotiations”, but he added that a deal is “still in the process of being formalised”. Mr Kerry has spent four months trying to get the two sides back around the table.

The veteran Palestinian chief negotiator Saeb Erekat and Israel’s interior minister, Tzipi Livni, who is responsible for negotiations with the Palestinians, are due in Washington this week, although it could be a number of weeks before face-to-face talks begin.

Mr Kerry stressed the need to keep details of the deal secret but, in the crucible of Middle Eastern politics, elements of what has been agreed emerged almost as he finished unveiling the new initiative. It is believed that the Palestinian leadership will now put on hold a plan to ask to ratify a number of United Nations treaties and will not pursue Israel through the International Criminal Court in The Hague.

But any rapprochement between the two sides remains fragile and riddled with suspicion.

The most difficult aspect of the Kerry plan for both parties may be internal opposition, however. Gaza continues to be governed by the militant Hamas faction, which refuses even to recognise Israel’s existence, while some members of the more moderate Fatah, which dominates the governing Palestinian Liberation Organisation, refuse to recognise Israel as a Jewish state.

There is also deep-rooted opposition on the Israeli side. The country’s trade minister, Naftali Bennett, has threatened to withdraw from Benjamin Netanyahu’s ruling coalition, while any future land concessions are likely to enrage settler groups and the three settlers in the Israeli cabinet.

There was international praise for the two sides and Mr Kerry yesterday. A spokesperson for Tony Blair’s Office of the Quartet Representative, which works to boost economic development in the Palestinian territories, said: “We welcome the announcement of the resumption of talks. We look forward to working with all the parties to ensure the full potential of two viable states is realised.”

William Hague, the Foreign Secretary, said: “I pay tribute to the efforts of Secretary Kerry and his team and I commend the leadership shown by both Prime Minister Netanyahu and President Abbas.”

* This story has been amended to make clear that the view of the prisoners as ‘political’ is disputed.