Aaron David Miller is a vice president and distinguished scholar at the Woodrow Wilson International Center for Scholars and author of "The End of Greatness: Why America Can't Have (and Doesn't Want) Another Great President." Miller was a Middle East negotiator in Democratic and Republican administrations. Follow him @aarondmiller2 . The opinions expressed in this commentary are his.

(CNN) It is somewhat ironic that Donald Trump's commitment to cut the ultimate conflict-ending deal between Israel and the Palestinians is coinciding with the 50th anniversary of the 1967 war -- an occasion that also grimly marks a half-century of failed US diplomatic efforts to do the same.

On June 5 of that year, in response to escalating tensions with Syria (amidst Soviet disinformation that Israel was mobilizing to strike ) and Egypt's large-scale deployment of forces into Sinai and its closure of the Straits of Tiran, Israel launched what would become known as the Six Day War. In a campaign that lasted only 132 hours, the Israelis would defeat Arab military forces and come into possession of the West Bank; Gaza; East Jerusalem; the Golan Heights and Sinai. The issues raised by that war have never been resolved.

This is not to say that US diplomacy hasn't been critically important in the transformation of the Arab-Israeli arena post-1967.

Henry Kissinger negotiated a 1974 disengagement agreement between Israel and Syria which, until very recently, made that border one of the quietest on the confrontation line.

It was Jimmy Carter who brokered the 1979 Egyptian-Israeli peace treaty; and Bill Clinton who played an important supportive role in helping Israelis and Jordanians to do the same in 1994.

But when it comes to Israeli-Palestinian peace, America hasn't even come close.

Having played a very small role in this rather large enterprise for a good many years, I've developed some pretty strong views as to why America -- the most important external actor in this drama -- hasn't been able to deliver a conflict-ending accord.

JUST WATCHED Jimmy Carter hopes Trump pushes Mideast peace Replay More Videos ... MUST WATCH Jimmy Carter hopes Trump pushes Mideast peace 02:31

Here are my top five. President Trump and his team might want to take notes, because these same pesky challenges are almost certain to get in their way, too.

This isn't just a real-estate deal

Israeli-Palestinian peace makes the peacemaking process between Israel and the Egyptians and Jordanians look like a walk in the park. Those were accords between established states with strong governments largely over security and readjusting borders; not between an established state and a divided, dysfunctional national movement seeking to become one in a turbulent unsettled region.

Then there's the complication of being too close to each other. Unlike Jordan, Egypt and Israel, Palestinians and Israelis have a real proximity problem. I remember, as part of the 1997 interim negotiations, being down on my hands and knees measuring the width of a street in Hebron as angry Israeli settlers and Palestinians looked on, thinking to myself this can't possibly work.

JUST WATCHED Hamas leader: Trump has 'historic opportunity' Replay More Videos ... MUST WATCH Hamas leader: Trump has 'historic opportunity' 04:11

And unlike the two other peace treaties, cutting the ultimate deal means not just dealing with territory but with three other tortuously complicated identity issues -- Jerusalem, Palestinian refugees, and recognition of Israel as the nation state of the Jews.

These aren't just 1967 matters -- they go back to 1948 and are foundational in the religious and political narratives of both peoples and faiths. Throw in the settlements and almost 500,000 Israelis living on land claimed by both sides and you see why Trump needs to study up some more. This problem is harder, not easier, than most people think.

You need leaders

Without exception, the serious breakthroughs in Arab-Israeli negotiations post-1967 occurred because there were leaders who were more masters of their politics and ideologies than prisoners of them.

Sure, Jordan's King Hussein, Egypt's Anwar Sadat and Israel's Menachem Begin and Yitzhak Rabin were never free agents. Both Sadat and Rabin would pay with their lives for their peacemaking. But they were determined to exploit or react to opportunities, and in doing so, rose above the narrow confines and drudgery of the conflict. None were peaceniks; they were all hard men and transformed hawks. We don't have those leaders today anywhere in the region -- certainly not in Israel and Palestine.

JUST WATCHED Abbas: With Trump's wisdom, peace is possible Replay More Videos ... MUST WATCH Abbas: With Trump's wisdom, peace is possible 00:46

Both Palestinian Authority President Mahmoud Abbas and Israeli Prime Minister Benjamin Netanyahu lack vision and are too risk-averse, tied to their politics, and more interested in keeping their seats than in jeopardizing them by trying to fundamentally change the status quo. Trump needs to understand that a willful and skillful mediator is critical, but much more important are partners willing to make decisions that allow a third party to bridge gaps. On the core issues, Abbas and Netanyahu are not even close.

And real ownership, too

Every breakthrough post-1967 -- even those negotiations that never came to fruition, like the Oslo and Israeli-Syrian talks -- required urgency and the presence of both pain and gain that would give the leaders a stake in trying to move ahead.

Sadly, it was war and insurgency that would lead to both the Israeli-Egyptian and Israeli-Jordanian peace treaties. In launching his attack in October 1973, Sadat knew that if he were to recover Sinai, he needed to come to the table as a victor, not the vanquished. And it was the first intifada that generated the Oslo process and allowed King Hussein to make his own deal with Israel, since the PLO's Yasser Arafat was negotiating directly with the Israelis for his.

JUST WATCHED From Sputnik to the Cuban Missile Crisis Replay More Videos ... MUST WATCH From Sputnik to the Cuban Missile Crisis 06:03

It's also a stunning fact that in all these negotiations, the initial breakthroughs occurred secretly, without the knowledge of Washington. While on vacation in August 1993, I vividly remember the call from the State Department Ops Center summoning me back to Washington because Israel and the Palestine Liberation Organization (PLO) had reached an agreement. We knew about the Oslo channel, but not that the two sides were ready to make tough decisions.

Can the US act as an honest broker?

In 2005, I wrote a piece in The Washington Post titled "Israel's Lawyer," in which I argued that at the Camp David July 2000 summit, the US side -- myself included -- had far too often taken Israel's side in the negotiations. I actually had borrowed the term from Kissinger's memoirs. The article was hijacked by all sides, particularly by those seeking to demonstrate that the US was in Israel's pocket.

JUST WATCHED Trump keeps US embassy in Tel Aviv for now Replay More Videos ... MUST WATCH Trump keeps US embassy in Tel Aviv for now 01:10

The real point that I was making was that the US can function -- and often has functioned -- as an effective broker in certain circumstances but rarely as a strictly honest and unbiased one.

Kissinger could negotiate three disengagement agreements between Israel, Egypt and Syria by backing off of a pro-Israel script and the urgency of the war; Carter could broker an Egyptian-Israeli peace treaty by clearly meeting Sadat's needs, but only because Egyptian leaders were ready to cut a separate deal and jettison the Palestinians and Syrians, thus playing to Israel's requirements, too.

It remains very much an open question as to whether the US can do the same between Israel and the Palestinians given the nature of our special relationship with Israel, US domestic politics, the sensitivity and degree of difficulty of the issues. The peculiar nature of the Palestinian national movement that looks like Noah's Ark, in which there are two of everything split between Hamas and Fatah -- security services, mini-statelets, and visions of what Palestine is and where it should be -- also poses difficulties.

What would be required at a minimum to help the facilitator would be an Israeli prime minister willing and able to make big moves and a Palestinian president to respond in kind.

Follow CNN Opinion Join us on Twitter and Facebook

President Trump does have certain advantages because he's new to the presidency. He's unpredictable and is capitalizing on a new alignment between Israel and the Arabs, particularly the Saudis. This may well be enough to begin a process. But it still leaves open the question: Toward what end?

The gaps on the core issues -- June 1967 borders, Jerusalem, refugees, security arrangements -- are Grand Canyon-like; the mistrust and suspicion are deep; and America's reluctance to use both honey and vinegar to move the parties, particularly the Israelis, is still pretty strong.

Never say never. But you'd need a miracle in a region that hasn't seen many for quite some time. Fifty years after 1967, the road ahead is at best uncertain, waiting perhaps for leaders to rise to the challenge of resolving the problem of the (much too) promised land.