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) Sean Spicer's cautious comments at the White House press briefing on moving the US Embassy to Jerusalem suggest that the incoming Trump administration is taking its time considering whether to make good on the President's campaign promise.

And it's just as well. For an administration that aspires to an America First foreign policy, moving the US Embassy to Jerusalem puts America's interests last, not at the head of the line.

Whatever the political benefits of moving the embassy from Tel Aviv to Jerusalem, it's hard to see the compelling US national interests that would warrant the change and outweigh the risks of doing so.

Rarely, though, has an incoming administration seemed so serious about acting on its campaign pledge. Trump has made the pledge repeatedly. He has nominated an ambassador who already has personally endorsed the move -- and written into the statement announcing his appointment that he was looking forward to representing the US from a Jerusalem embassy.

Indeed, having worked the Middle East in both Republican and Democratic administrations, it's never seemed more apparent that the incoming administration wants to initiate the move. The issue appears to be not whether, but when and how.

The Trump administration's motives for raising the controversial Jerusalem issue now are varied. It would show that Trump is serious about his campaign promises; it would demonstrate a sharp break with the tensions that marked the previous administration's relations with Israel; and it would show support for a close US ally.

Finally, the incoming administration is eager to correct a legitimate anomaly -- Israel is one of the few countries in the world in which the US doesn't maintain its embassy in the preferred capital of the host country where the parliament, Supreme Court and seats of government are located.

As relevant as these political considerations may be, none of them outweigh the downsides of the move from a national security or foreign policy perspective. There are many ways to reassure the Israelis of US support without undertaking a unilateral change in US policy that accrues little real benefit to America.

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Instead, the downsides are painfully obvious. The move will signal -- no matter how it's explained -- that the US is validating Israel's claims to the entire city of Jerusalem, signaling that the Trump administration has green-lighted what is certain to be an intensification of Israeli building in the east, pre-judge Palestinian claims to what is undeniably the most combustible and explosive issue in the unresolved Israeli-Palestinian conflict and compel Palestinians and Arab states to mount a defense of Jerusalem, which will invariably focus on the holy sites and stir up religious passions.

How much violence there might be is impossible to predict, though it's clear that Israeli security professionals are worried about the consequences.

With the peace process all but dead and the prospects for implementing a two-state solution slim to none anytime soon, it's hard to argue that moving the embassy will somehow kill a process that's already comatose.

What it will do is undermine US credibility and authority as an effective -- let alone honest -- broker in any negotiations not just with Palestinians but with key Arab states as well. After all, moving the embassy is something the US is doing, not Israel.

The Arabs have more important issues such as Iran and ISIS to discuss with the US, so they may try to contain their reaction. Still, the defense of Arab Jerusalem will play easily into the hands of Iran and the Sunni jihadists, who will use it to embarrass and attack both the Arab states and America.

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Trump fashions himself the transactor-in-chief -- a negotiator who always gets something for what he gives. In this case, it's hard to see exactly what America is getting for a unilateral change in policy that involves a significant amount of risk.

The US will clearly reassure the current Israeli government that it is different than the Obama administration -- and every other US administration -- and satisfy a number of domestic constituencies at home. But is any of this worth the potential cost?

Bottom line: There is simply no compelling justification to move the US Embassy or the ambassador to Jerusalem now -- and many more very good reasons not to.