Washington's top diplomat was holding talks on security with Israeli Prime Minister Benjamin Netanyahu on Thursday in their first meeting since a fallout over a nuclear deal struck with Iran.
US Secretary of State John Kerry landed just before midnight (2200 GMT) on Wednesday for a trip aimed at giving momentum to the direct negotiations, which appear to have made little headway since they began under his patronage in late July.
But his meeting comes at a point of high tension with Israel over the November 24 Iran deal, which saw the Islamic republic agreeing to roll back parts of its nuclear programme in return for limited sanctions relief - in a move loudly denounced by Netanyahu as a "historic mistake".
Kerry was to hold talks in Jerusalem at 0730 GMT with Netanyahu then head to Ramallah in the West Bank to meet Palestinian president Mahmud Abbas for a meeting at 1200 GMT, officials said.
His morning meeting with Netanyahu will focus squarely on Israel's security needs in the framework of a peace deal, and will see the Israeli leader receiving his first briefing from US special envoy on security General John Allen, US officials said.
US and Israeli media reports have suggested that Allen was to present Netanyahu with an outline of how Israel's security arrangements might look as part of a peace deal with the Palestinians.
"Secretary Kerry and General Allen will be providing an update on their evaluation of Israel's security as part of the meeting," a senior State Department official said late on Wednesday.
Another State Department official said the update would "include many details and specifics" but denied that Allen, who will be briefing Netanyahu for the first time, was to present him with a ready-made plan.
"He is providing an update (which will) include many details and specifics. This is obviously an ongoing discussion about Israel's security.. it's not to present a plan," the official said.
Kerry would also be giving Netanyahu an update on the "first-step" Geneva agreement with Iran and the talks under way to reach a comprehensive deal.
"He will certainly be providing an update and a briefing on... the P5+1 negotiations, the first step that was agreed to, as well as the path forward to a comprehensive agreement," an official said.
Israel and the West believe that Iran's nuclear programme is a front for developing a weapons capability, a charge Tehran has repeatedly denied.
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The Islamic republic has a long history of belligerent statements toward the Jewish state, which has warned that a nuclear Iran would pose a existential threat to Israel.
But US assurances that the Geneva deal would ultimately result in a more secure Middle East have not been well received in Israel.
"While there is certainly a disagreement over tactics - as we all know, the Israelis had supported an effort to have a comprehensive agreement - we felt a first step was the only viable path forward," the US official said.
"We are now negotiating comprehensive steps," he said.
Iran fallout 'not impacted' peace process
Another official said despite the disagreements, the two were expected to hold a "robust dialogue" on the issue.
But he denied the fallout over Iran had impacted Israel's willingness to properly engage in the US-sponsored talks with the Palestinians.
"It has not impacted the process. There are other aspects that have certainly impacted the process over the past couple of weeks that we're all well aware of, right. But this particular piece, the discussions on Iran... have not."
His remarks referred to a series of major Israeli settlement announcements, which have embittered the atmosphere between the sides and threatened to derail the talks, which began in late July with the ambitious aim of securing a deal within nine months.
With the talks almost at the half-way point, the Palestinians have warned that if the negotiations fail, they would revive efforts to seek international recognition, which have currently been frozen.
"The talks are going through great difficulties because of the obstacles created by Israel," Abbas said on Monday.
"The commitment to refrain from action at the United Nations ends after the nine-month period."