WASHINGTON — Under the best of circumstances, a Mideast peace deal is the Holy Grail of diplomacy, a goal that has eluded American presidents for generations.

With Israeli Prime Minister Benjamin Netanyahu set to visit Washington this coming week, the mix of politics, personalities and historical grievances that has stood in the way of Israeli-Palestinian peace is even more combustible than normal.

President Donald Trump’s point man for mediation, Jared Kushner, is in the middle of a political firestorm, his plan remains a mystery and the Palestinians aren’t even speaking to the White House. If that weren’t enough, Netanyahu and Trump are both distracted by mushrooming legal investigations at home.

It’s all contributing to an intensified pessimism in the U.S., Israel and the West Bank about prospects for a Trump-brokered initiative to succeed.

Kushner and a small team have spent the past year preparing a much-awaited blueprint for peace, but no details have emerged. Many in the region wonder whether the vaunted plan will ever come.

On the surface, Israel’s relationship with the White House has never been better, buoyed by the Jewish state’s thunderous support for Trump’s decision to relocate the U.S. Embassy in Jerusalem and recognize the disputed city as Israel’s capital. The announcements only reinforced Palestinians impressions of Trump as biased against them.

“A mediator will have to mediate between two semi-equal parties. Otherwise it’s not a mediation process,” said Husam Zomlot, the Palestinian ambassador to Washington, in a recent Associated Press interview. “You have to level the field and level your relationship between the two sides in order to be an honest mediator.”

The world may soon be able to judge for itself.

The Trump administration’s peace proposal is near completion, according to U.S. officials, but faces an uncertain future as Kushner, the Trump son-in-law leading the effort, recently lost his top-secret security clearance. Former negotiators say Kushner’s downgraded status probably will severely impair his ability to do the job.

Beneath the veneer of U.S.-Israeli unity, there is lingering disagreement and suspicion.

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Israel is increasingly worried that Trump is backsliding on a pledge to “fix” or dismantle the 2015 Iran nuclear deal. Israel also is concerned that behind Trump’s tough public stance toward Tehran is an acquiescence to Iran’s growing presence in Syria and influence in Lebanon — two Israeli neighbors.

“The Israelis now are undoubtedly sounding the alarm,” said Jonathan Schanzer, who researches Iran’s regional influence at the hawkish Foundation for the Defense of Democracies. “The assets the Israelis see on the other side of the border to its north — they are not happy.”

Nevertheless, it’s in Netanyahu’s interest to keep such disputes out of the public eye, said David Makovsky, a former State Department official who worked on Mideast peace negotiations. The Israeli leader faces multiple investigations related to allegations of bribery and corruption.

“It’s important for him not to run afoul of Trump,” said Makovsky, now at the Washington Institute for Near East Policy. “It’s necessary for him to show he’s not so engulfed by his own legal problems that he’s not functioning as a leader.”

Trump and Netanyahu are scheduled to meet Monday, in the middle of the annual American Israel Public Affairs Committee policy conference, which brings thousands of pro-Israel officials, lawmakers, activists and academics to Washington.

Vice President Mike Pence, U.N. Ambassador Nikki Haley and Trump’s envoy to Israel, David Friedman, will give speeches, and each is likely to hammer away at Iran.

Israel views Iran as an existential threat and Netanyahu has repeatedly implored Trump to “fix it or nix it” when it comes to the nuclear deal. That agreement, negotiated by the Obama administration and other world powers, rewarded Iran with billions of dollars in sanctions relief for curbing its nuclear program.

Critics, including Netanyahu and Trump, say Tehran got too much for too little. Among the remedies they’re advocating: removal of several of the deal’s clauses that allow Iran to gradually resume advanced nuclear work starting in 2024.

Trump has said he won’t renew U.S. waivers for sanctions when they next expire on May 12 unless European countries agree to a new deal that would force them to punish Tehran if the Iranians resume advanced nuclear work. He wants tougher inspections and penalties for Iranian missile testing. He also wants Europe to punish Iran’s support for the anti-Israeli militant group Hezbollah, Yemen’s Houthi rebels and Syrian President Bashar Assad’s government.

Israeli officials are most immediately concerned about Iran’s missile work. They want U.S. and European commitments to punish Iran for work on medium-range missiles capable of hitting Israel and Iran’s Arab rivals. The Europeans have balked, citing U.N. restrictions that focus only on longer-range projectiles. U.S. officials negotiating with Britain, France and Germany appear to agree with the Europeans, prompting the Israeli concern.

Trump’s Mideast peace aspirations aren’t any more certain. After winning praise in Israel for his Jerusalem proclamation, he made clear the Israelis would have to make concessions, too. He hasn’t said what those might be.

“You won one point, and you’ll give up some points later in the negotiation, if there’s ever a negotiation,” Trump said in January.