With North Korea’s successful testing of an intercontinental ballistic missile that might be able to reach parts of the United States, Donald Trump is facing a foreign-policy challenge of the first order. But, at a press conference in Warsaw on Thursday, where he appeared alongside Andrzej Duda, the President of Poland, Trump refused to be drawn out on what he might do in response. “I have some pretty severe things that we are thinking about,” he said. “That doesn’t mean we are going to do it. I don’t draw red lines.”

That’s not true, of course. In January, when North Korea’s leader, Kim Jong-un, announced that his military forces had “reached the final stage in preparations to test-launch an intercontinental ballistic rocket,” Trump’s response was rapid and seemingly definitive. “North Korea just stated that it is in the final stages of developing a nuclear weapon capable of reaching parts of the U.S.,” he said on Twitter. “It won’t happen!”

Six months later, it does appear to be happening, and North Korea may still have more provocations in store. On Wednesday, the South Korean defense minister, Han Min-koo, told a parliamentary committee in Seoul that Kim might be about to carry out a nuclear warhead test. “The Kim Jong-un regime tends to launch a ballistic missile followed by a nuclear test as a package of nuclear provocations, and the G-20 summit can be a perfect time to shock the world again,” Han said. At his press conference in Warsaw, Trump said that North Korea was “behaving in a very, very dangerous manner.” But he kept his language vague. “It’s a shame they are behaving this way . . . something will have to be done about it,” he said.

Behind this reticence was a tacit admission that his attempt to rely on China to exert pressure on the North Korean regime is looking tattered. Indeed, Trump himself has admitted this much: “So much for China working with us - but we had to give it a try!” he tweeted on Wednesday, before setting off on his trip to Europe.

Of course, Trump isn’t the first President to have struggled with the North Korean issue. Bill Clinton, George W. Bush, and Barack Obama all searched in vain for a way to stop Pyongyang’s drive for nuclear weapons. But none of Trump predecessors made a declaration like the one Trump issued in January. As Simon Jenkins, a former editor of The Economist and the London Times, commented in the Guardian, “The trouble with issuing ultimatums around the globe is that they invite the reckless to call your bluff and make you look a fool.”

At the G-20 summit, which is taking place in Hamburg on Friday and Saturday, we can be pretty sure that none of the assembled leaders will use such dismissive language to refer to the American President. But Trump is facing a credibility problem. At times during the Obama Presidency, such as the Syria crisis of 2013, some foreign governments wondered whether the United States had lost the desire to exert global leadership. But these doubts were nothing compared to the worldwide concerns about the quality, consistency, and motivations of American decision-making under Trump.

Appearing on CNN on Wednesday, Richard Haas, the president of the Council on Foreign Relations, argued that the Trump Administration has three options in regard to North Korea’s nuclear ambitions: acceptance, military intervention, or negotiation. Not one of these options is particularly attractive, and they all present immense challenges.

The first option would involve the U.S. government recognizing that North Korea had joined the club of nuclear armed states, and then relying on the threat of a massive retaliation to deter a nuclear attack on the United States, South Korea, or Japan. Given the recent advances in North Korea’s missile capability, and the fact it has stockpiled enough nuclear material for dozens of warheads, some defense experts believe that this is the most realistic course of action. Partly because of Trump’s hard-line statements, however, it doesn’t seem to be under serious consideration by the Administration—at least for now.

The second option, intervention, also seems unlikely—despite some saber-rattling by the Pentagon, which responded to the North Korean missile test by launching a live-fire exercise with the South Koreans. Kim’s nuclear capabilities are dispersed, and the North Korean military has huge artillery batteries trained on Seoul, meaning that for any U.S.-led strike to be effective, it would have to be a major. Such an attack would almost certainly lead to a full-scale war, with many casualties. “This idea that there this something small and surgical needs to be dispensed with,” Haas noted.

That leaves direct negotiations with Pyongyang, which China and Russia are pressing for. Earlier this week, when President Xi Jinping met with Vladimir Putin in Moscow, they proposed a halt in military operations and testing by all parties on the peninsula, including the United States, which is installing a missile-defense shield that North Korea and China both strongly oppose. Once this freeze is in place, talks between the two sides could begin.

While a negotiated settlement that denuclearized the two Koreas would appear to be the best possible outcome, achieving such an agreement would tax a Metternich, let alone a Trump. Even getting the talks started would involve both sides making big concessions. Ever since the nineteen-nineties, when the Clinton Administration failed to get Pyongyang to halt its nuclear program, the U.S. government has made denuclearization a precondition for further negotiation. North Korea, too, would have to depart from its publicly stated position. Earlier this week, according to a report from the official North Korean government news agency, Kim told an audience of military scientists that his government “would neither put its nukes and ballistic rockets on the table of negotiations . . . nor flinch even an inch from the road of bolstering the nuclear force chosen by itself unless the U.S. hostile policy and nuclear threat to the D.P.R.K. are definitely terminated.”

For now, the Trump Administration doesn’t appear to be pursuing any of these three options. Instead, it is trying to ramp up the pressure on Kim by getting the United Nations to impose more punitive economic sanctions on North Korea. But this strategy depends on securing the support of China and Russia, neither of which seems willing to go along, especially if it would be seen as buckling to U.S. demands.

Trump is scheduled to meet with both Xi and Putin on Friday at the G-20 summit. He will take into these meetings the baggage of his domestic problems, his ill-considered tweets, and his nihilistic statements about America’s place in the world. It is to be hoped that he is finally realizing that America can’t afford to go it alone. But with Trump hopes are seldom realized.