WASHINGTON - Iran's announcement on Monday that it expects to breach the terms of the 2015 agreement that was intended to slow its ability to develop a nuclear weapon opens a new and perilous phase of its confrontation with the West.
If the Iranians make good on their threat to break through the restrictions on how much nuclear fuel they will produce, Tehran will have enough fuel to make a single bomb in less than a year for the first time since the 2015 agreement went into effect. The one-year buffer is the safety threshold that the Obama administration set and that the Trump administration has adopted to impede Iran from gaining the capability to build a nuclear weapon.
Iranian leaders appear to be testing whether the rest of the coalition that negotiated the nuclear deal - especially the big European powers - will stick with Washington.
Should the Europeans break with the Trump administration and agree to help Iran weather harsh economic sanctions imposed by the United States, Tehran said, it could avoid breaking the 2015 agreement. That seems unlikely.
Nonetheless, the Europeans blame President Trump for pushing Iran into breaking out of an agreement that was working, as do China and Russia. And despite calls from some hawks in Washington for military action - most recently Senator Tom Cotton, Republican of Arkansas, who said on Sunday that attacks on tankers in the Gulf of Oman "warrant a retaliatory military strike" - Iran is betting that this time Washington will find few allies willing to escalate the confrontation, either in the Persian Gulf or by attacking the country's nuclear facilities.
It is a huge game of chicken, and a miscalculation on either side could easily provoke a conflict.
Now Mr. Trump faces two immediate challenges: making the Persian Gulf safe for oil shipments and keeping Iran from edging toward the bomb-making capability that incited the crisis of a decade ago. Neither will be easy.
"Unfortunately, we are heading toward a confrontation," Iran's ambassador to Britain, Hamid Baeidinejad, warned CNN's Christiane Amanpour on Monday.
But it is also part of the unwinding of Mr. Trump's promise that he would restore respect for American power to the degree that adversaries would give up their nuclear weapons programs, starting with North Korea, to be followed by Iran.
Nearly two and a half years into his presidency, Mr. Trump's high-profile diplomatic effort with North Korea has stagnated, and Kim Jong-un, whom the president improbably declared a friend who will make good on his promises, is assessed by American intelligence agencies to be adding to the North's arsenal while the clock ticks. On Monday, President Xi Jinping of China announced that he plans to visit North Korea this week, his first trip there as president.
At the same time, Mr. Trump's gamble that Iran would crack once he abandoned the Obama-era nuclear deal and reimposed sanctions has failed to pay off, at least for now.
Instead the Iranians escalated, leaving Mr. Trump without any easy options. That is in part because the confrontation erupted so quickly, and in part because Mr. Trump is paying the price for having alienated so many other participants in what was once an international coalition to isolate Iran's leaders.
"The U.S. seems to have embarked on its 'maximum pressure' campaign with few allies and little forethought as to unintended consequences or how to respond if key assumptions - e.g., that Iran will implode or succumb and enter talks on U.S. terms - prove false," Brett McGurk, Mr. Trump's former special envoy for the global coalition against the Islamic State, wrote recently.
He added: "Those assumptions are now highly questionable at best, which means the entire policy foundation as articulated by Trump has eroded. Iran appears to have made the strategic decision (not surprising) to resist economic pressure and respond asymmetrically, not directly against us."
Iran has almost never directly taken on American forces, knowing what the result would be. Instead, it has used proxies like Hamas, the Palestinian organization judged by the United States to be a terrorist operation, while also launching cyberattacks and building missiles that could reach American allies but not the United States.
In striking the 2015 nuclear agreement, President Barack Obama was betting that he could gradually encourage Iran to moderate that behavior. The effort failed - the Islamic Revolutionary Guards Corps, keeper of the nuclear program, turned its attentions elsewhere. But the agreement deprived Iran of a pathway to a nuclear weapon for another 15 years or so.
Mr. Trump has taken the opposite approach, trying to force change by choking off every last source of oil revenue. He abandoned the nuclear accord so that he could reimpose sanctions - while his administration insisted that Iran must still adhere to the accord. And Mr. Trump has prematurely claimed victory, declaring that Iran is "a different country" since he began to crack down.
Mr. Trump has few easy options as he confronts the challenge of keeping tanker traffic moving through the Persian Gulf while also facing Iran's provocative nuclear stance.
Securing the gulf requires enough naval vessels and reconnaissance capability to monitor just about everything passing close to Iran's shores.
"That requires a coalition," said John F. Kirby, a retired rear admiral who participated in the tanker wars of the 1980s and served as the State Department spokesman during the negotiation of the Iran deal. "We don't have enough ships to do it ourselves."
Whether the United States can convince allies to supply additional ships may be a test of how big a price Mr. Trump has paid for alienating the other nations that were part of the 2015 agreement and that also fear Iran's move to a bomb.
Secretary of State Mike Pompeo suggested on Sunday that China, among others, should help with that task, since it is so dependent on oil from the Middle East. But it is far from clear that China, Russia or the three European powers that negotiated the nuclear accord alongside the United States - Britain, France and Germany - are willing to join in that effort.
But the longer-term challenge is whether the world will still unite around the idea that Iran cannot be trusted with anything more than a token nuclear capability.
With Monday's announcement, Iran has made it clear that it plans to increase the pressure, first by producing more uranium, then by gradually ramping up the enrichment level of the nuclear fuel, pushing it closer and closer to bomb grade.
Tehran appears to be betting it can do that, gaining leverage over the West, without prompting a military response. That was a close call in Mr. Obama's time, when plans were drawn up for such an attack. In the Trump era, it is as unpredictable as a president who says he does not want another war in the Middle East, but periodically threatens one.