Hours before flying to Washington to try to scuttle an emerging US nuclear deal with Tehran, Prime Minister Benjamin Netanyahu made a high-profile visit Saturday to Judaism’s holiest prayer site.

Wearing a black skullcap, he rested his hands on Jerusalem’s Western Wall while praying briefly, before turning to face a bank of microphones.

“I would like to take this opportunity to say that I respect US President Barack Obama,” he said.

“I believe in the strength of the relations between Israel and the United States,” he said. “That strength will prevail over differences of opinion, those in the past and those yet to come.”

Netanyahu has infuriated the White House and Democrat lawmakers by accepting an invitation by Republicans to speak on Capitol Hill on Tuesday.

“As prime minister of Israel it is my duty to care for the security of Israel,” he said. “That is why we strongly oppose the agreement emerging between Iran and the world powers which could endanger our very existence.

“In the face of this danger we must unite and also explain the dangers stemming from this agreement, to Israel, to the region and to the world.”

US Secretary of State John Kerry will leave at the weekend for Switzerland for another meeting with his Iranian counterpart Mohammad Javad Zarif.

Zarif said Saturday that Netanyahu would not be able to prevent a deal from going forward.

“I believe this effort is fruitless and it should not be an impediment to an agreement,” he said at a joint press conference with his visiting Italian counterpart Paolo Gentiloni.

“It is unfortunate that there is a group which sees its interests in tension and crisis.”

Iranian Foreign Minister Mohammad Javad Zarif (right) shakes hands with US Secretary of State John Kerry (left) in Geneva, January 14, 2015. (photo credit: AFP/Rick Wilking/Pool)

The pace and intensity of the talks have increased as global powers gathered under the P5+1 group have sought a deal with Iran to stop it acquiring a nuclear weapon — something Tehran denies trying to do.

A March 31 deadline for a political framework for the deal is looming, with negotiators saying they will aim to pin down the final technical details by June 30.

Israel believes the sides are likely to reach an agreement that eases international sanctions on the Islamic republic without applying sufficiently stringent safeguards to stop it developing nuclear weapons.

Netanyahu’s US trip also comes just two weeks before Israel’s March 17 general election in which he is seeking a third consecutive term in office.

The Western Wall in the Old City of east Jerusalem is the last remnant of the supporting wall of the biblical Jewish temple, built by King Herod and destroyed by the Romans in 70 AD.

Senior officials in the Obama administration charged Friday that while the Israeli leader was vehemently opposed to the emerging agreement, he has failed to present an alternative.

The officials told reporters during a briefing that an imperfect deal with Iran to curb its nuclear program by freezing its efforts for a time was preferable to a breakdown in talks which could see Iran race for the bomb, according to the New York Times.

“The alternative to not having a deal is losing inspections, and an Iran ever close to having the fissile material to manufacture a weapon,” a US official told the paper.

But concerns against the proposed deal include an ability for Iran to resume its efforts in the last years of a phased agreement and to be closer to the bomb than it is now in those years — two or three months rather than a required year, which is one of the US’s demands in the first stage of the agreement.

Officials were also unclear about when and how Iran would have to respond to questions by the IAEA about its nuclear program.

“We have made a substantial amount of progress. Ultimately, Iran has to make a very significant political decision to allow the flexibility to close this deal,” the official told the NYTimes.

The US on Friday set out what it called its “bottom lines” to reach a deal, ahead of new talks next week which are reported to be progressing.

A view of Iran's Bushehr nuclear reactor (Photo credit: Youtube screen capture)

Staking out the broad outlines of a deal Friday — without going into specifics — another US official spelled out where Washington was standing firm:

— Iran should not be allowed to develop weapons-grade plutonium at its Arak reactor. “We’re discussing how Iran can convert that Arak reactor to serve a different purpose,” the official said.

— Iran should not use its Fordo nuclear plant to enrich uranium; that would leave only Iran’s Natanz plant capable of enriching uranium, which at high grades can be used in nuclear weapons.

— Any deal must ensure that it would take Iran a year to gather enough fissile material to make a bomb.

— Iran would “reduce significantly” its current number of operating centrifuges and its domestic stockpile.

— Iran must agree to unprecedented inspections of both nuclear and production facilities as well as uranium mines and mills, and suspect sites.

— The US is pursuing a deal in which relief from international sanctions demanded by Iran “is phased in over a period of time.”

“We are insisting on the principle that sanctions can snap back into place if Iran were to violate the agreement,” the US official said.