President Donald Trump’s wild and woolly press conference at the end of the G-7 summit shows, once again, that the putative author of The Art of the Deal is a lousy negotiator.

It’s one thing, and fairly risky, to go all-out “maximum pressure” on China and Iran, but at least that’s a strategy. It’s another thing, and simply bumbling, to do so, then to admit having “second thoughts” about escalating tariffs against China (then to have a spokesman backpedal on that) and to welcome a dialogue with Tehran (only to have President Hassan Rouhani blow him off).

Similarly, it’s one thing, though unconstitutional (and, therefore, a mindless bluff), to order U.S. companies to stop doing business with China, as Trump did just before the summit. But another then to say, at the press conference afterward, that President Xi Jinping is a “great leader” who will make a deal soon, and once he does, the companies should stay put and “do a great job.”

If you’re a corporate executive doing business in China, or an investor trading currencies, or even engaged in commerce almost anywhere in the world, what are you supposed to do? How are you supposed to plan even months, much less years, ahead? As Paul Krugman wrote in the New York Times, protectionism, though bad enough, can be accommodated, but “erratic protectionism” is the stuff of chaos and downfalls.

The fundamental problem with Trump’s meanderings is that he doesn’t know what he wants.

It’s not just finance and industry that Trump is running ragged; this erraticism also warps diplomacy and damages U.S. interests. Asked about his tendency to veer back and forth at the press conference, Trump replied, “It’s the way I negotiate. It’s done very well for me over the years, and it’s doing even better for the country.”

Well, no. It has not done very well for Trump over the years, unless you define “very well” as boosting profits by bilking suppliers and evading debt by declaring multiple bankruptcies. And neither technique has an analogue in the more complex arena of international politics.

In negotiating a contract or closing a real-estate deal, both sides—Trump and whoever is sitting on the other side of the table—have identical, though clashing, goals (to maximize revenue), and they’re both playing under the same rules and regulations.

In negotiating a trade deal or an arms control pact, each side has many different goals—relating not just to what an observer might regard as its national interests, but also to the interests of a wide array of domestic and bureaucratic factions, which might be difficult to placate and, in any case, often call for a shrewd and delicate approach. (That’s one place where intelligence agencies come in handy; too bad Trump ignores them.)

Let’s say Trump does have a full command of the situations involving China and Iran, and let’s say maximum pressure is a promising tactic. In order to make it work, he would have to stick with it. Yet to the extent Xi and Rouhani were ever shaking in their boots (a dubious premise), Trump’s wavering gives them solace—reassures them (correctly or not) that they can wait the crisis out, that either Trump will fold or the damage he’s doing to the U.S. economy will usher in a more stable administration.

The fundamental problem with Trump’s meanderings, I suspect, is that he doesn’t know what he wants. If Xi wanted to end the trade war now, it’s not clear what he would need to do to coax Trump to an armistice. Nor is it clear what Rouhani would need to do in order to get the sanctions on his country lifted. In both cases, Trump smashed up the works—imposing enormous tariffs on China, withdrawing from a multinational nuclear deal with Iran—believing the other side would simply fold in the face of America’s power and his own deal-making prowess.

He had no backup plan, no list of priorities about what he’d be more or less willing to trade away in some compromise—no sense that a compromise might be necessary.

China steals intellectual property and engages in unfair trade practices; this is unconscionable, and too many past presidents have done too little about it. But slapping 25 percent tariffs on all Chinese goods doesn’t address the problem and, in fact, distracts from a search for solutions. Iran funds terrorists and builds ballistic missiles with the range to attack U.S. allies, but pulling out of the 2015 nuclear deal—which had led to the dismantlement of Iran’s nuclear program—does nothing to address those problems either. (It would have been better to use the deal as the starting point for moving on to other issues, just as, during the Cold War, successive arms control treaties with the Soviet Union dealt with an ever-expanding set of disputes.)

One thing Trump’s shenanigans have done is demonstrate that the United States is still a powerful nation. Allied leaders, such as those at the G-7, have learned to treat him with kid gloves—to throw him compliments, laugh at his jokes, ply him with gifts—so he doesn’t do still more damage and, maybe, cooperates a little bit. But they have come to realize that, as long as Trump is in charge, the United States is an unreliable ally and that they would do well to find other arrangements—for security, trade, and other essentials in global politics—as quickly as possible. America’s competitors and adversaries—China and Russia, in particular—are detecting the cues, in some cases helping to widen the divide.

Trump is doing much more damage than he knows. At least some of those around him know this, but no one has the backbone to tell him.